No Enclosing Instance Of Type Is Accessible | Instanceof Java Keyword Tutorial 모든 답변

당신은 주제를 찾고 있습니까 “no enclosing instance of type is accessible – instanceof Java Keyword Tutorial“? 다음 카테고리의 웹사이트 https://chewathai27.com/you 에서 귀하의 모든 질문에 답변해 드립니다: https://chewathai27.com/you/blog. 바로 아래에서 답을 찾을 수 있습니다. 작성자 Alex Lee 이(가) 작성한 기사에는 조회수 34,459회 및 좋아요 1,441개 개의 좋아요가 있습니다.

no enclosing instance of type is accessible 주제에 대한 동영상 보기

여기에서 이 주제에 대한 비디오를 시청하십시오. 주의 깊게 살펴보고 읽고 있는 내용에 대한 피드백을 제공하세요!

d여기에서 instanceof Java Keyword Tutorial – no enclosing instance of type is accessible 주제에 대한 세부정보를 참조하세요

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The instanceof keyword returns true if what’s on the left is a class, subclass or interface of what’s on the right. Like this:
someObject instanceof someClass;
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no enclosing instance of type is accessible 주제에 대한 자세한 내용은 여기를 참조하세요.

What causes error “No enclosing instance of type Foo is …

I get No enclosing instance of type Hello is accessible.” at the line that creates a new Thing. I’m guessing either: I have system level problems (either in …

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Source: stackoverflow.com

Date Published: 6/8/2021

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No enclosing instance of type is accessible – Yawin Tutor

The java No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance …

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Source: www.yawintutor.com

Date Published: 4/24/2022

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java – What causes error “No enclosing instance of type Foo is …

Top 5 Answer for java – What causes error “No enclosing instance of type Foo is accessible” and how do I fix it? · Move Thing out of the Hello . · Change …

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Source: www.thecodeteacher.com

Date Published: 3/4/2022

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Java Error: No enclosing instance of type Main is accessible …

The following error occurred today while compiling a Java program. No enclosing instance of type Main is accessible.

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Source: programmerah.com

Date Published: 6/9/2021

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No enclosing instance of type is accessible. Must qualify the …

ERROR – No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ).

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Source: www.buggybread.com

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Java – No enclosing instance of type Foo is … – 程序员的小窝

Java – No enclosing instance of type Foo is accessible. 2021-6-3 anglehua. I have the following code: Hello { Thing { public int size; …

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No enclosing instance of type Class is accessible

Sáng nay ngồi code chơi gặp tình huống thế này. public A { public B{ private int num; public Date() { num = 0; } } public static …

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Java mutation error: no enclosing instance of type XXX is …

The meaning of error is , There are no external instances that can be accessed enclosing instance. You must assign an appropriate external  …

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How to fix “no enclosing instance of type is accessible”.

The cause: From your program I found that the of Thing was declared as a non-static inner . This implies that it must be …

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Java – No enclosing instance of type Foo is accessible

static Thing will secure your program work. As it is, you’ve got Thing as an inner , which (by description) is connected with a …

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주제와 관련된 이미지 no enclosing instance of type is accessible

주제와 관련된 더 많은 사진을 참조하십시오 instanceof Java Keyword Tutorial. 댓글에서 더 많은 관련 이미지를 보거나 필요한 경우 더 많은 관련 기사를 볼 수 있습니다.

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주제에 대한 기사 평가 no enclosing instance of type is accessible

• Author: Alex Lee
• Views: 조회수 34,459회
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• Date Published: 2020. 7. 2.
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What is no enclosing instance of type java?

The java No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ). exception happens when an instance is created for an inner class in the outer class static method.

Is not an enclosing class Java error?

In this situation the “not an enclosing class” error is due to incorrect use of this . this , within an instance method or constructor, refers to the current object. Using MainActivity. this is referring to the object MainActivity as if it were the current object but the current object is of type TestHandler .

How do you create an inner class in Java?

Creating an inner class is quite simple. You just need to write a class within a class. Unlike a class, an inner class can be private and once you declare an inner class private, it cannot be accessed from an object outside the class. Following is the program to create an inner class and access it.

What is static class in Java?

A static inner class is a nested class which is a static member of the outer class. It can be accessed without instantiating the outer class, using other static members. Just like static members, a static nested class does not have access to the instance variables and methods of the outer class.

What is use of static keyword in Java?

In Java, static keyword is mainly used for memory management. It can be used with variables, methods, blocks and nested classes. It is a keyword which is used to share the same variable or method of a given class. Basically, static is used for a constant variable or a method that is same for every instance of a class.

Is not an enclosing class intent?

not an enclosing class error is thrown because of your usage of this keyword. this is a reference to the current object — the object whose method or constructor is being called. With this you can only refer to any member of the current object from within an instance method or a constructor. Show activity on this post.

How do you make a class static?

We can declare a class static by using the static keyword. A class can be declared static only if it is a nested class. It does not require any reference of the outer class. The property of the static class is that it does not allows us to access the non-static members of the outer class.

Can inner class have constructor?

You can observe the constructor chain for the inner class when you extend an inner class. so you can see that you are able to call the super constructor of your nested class passing to that constructor the MainClass , and calling .

What is the difference between inner class and nested class?

In Java programming, nested and inner classes often go hand in hand. A class that is defined within another class is called a nested class. An inner class, on the other hand, is a non-static type, a particular specimen of a nested class.

How do you instantiate an inner class?

To instantiate an inner class, you must first instantiate the outer class. Then, create the inner object within the outer object with this syntax: OuterClass. InnerClass innerObject = outerObject.

What is inner class in Java with example?

In Java, inner class refers to the class that is declared inside class or interface which were mainly introduced, to sum up, same logically relatable classes as Java is purely object-oriented so bringing it closer to the real world.

What are static classes?

A static class is basically the same as a non-static class, but there is one difference: a static class cannot be instantiated. In other words, you cannot use the new operator to create a variable of the class type.

What causes error “No enclosing instance of type Foo is accessible” and how do I fix it?

You’ve declared the class Thing as a non-static inner class. That means it must be associated with an instance of the Hello class.

In your code, you’re trying to create an instance of Thing from a static context. That is what the compiler is complaining about.

There are a few possible solutions. Which solution to use depends on what you want to achieve.

Move Thing out of the Hello class.

Change Thing to be a static nested class. static class Thing

Create an instance of Hello before creating an instance of Thing . public static void main(String[] args) { Hello h = new Hello(); Thing thing1 = h.new Thing(); // hope this syntax is right, typing on the fly 😛 }

The last solution (a non-static nested class) would be mandatory if any instance of Thing depended on an instance of Hello to be meaningful. For example, if we had:

public class Hello { public int enormous; public Hello(int n) { enormous = n; } public class Thing { public int size; public Thing(int m) { if (m > enormous) size = enormous; else size = m; } } … }

any raw attempt to create an object of class Thing , as in:

Thing t = new Thing(31);

would be problematic, since there wouldn’t be an obvious enormous value to test 31 against it. An instance h of the Hello outer class is necessary to provide this h.enormous value:

… Hello h = new Hello(30); … Thing t = h.new Thing(31); …

Because it doesn’t mean a Thing if it doesn’t have a Hello .

For more information on nested/inner classes: Nested Classes (The Java Tutorials)

No enclosing instance of type is accessible – Yawin Tutor

The java No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ). exception happens when an instance is created for an inner class in the outer class static method. The static method attempts to create an object of an inner class that belongs to an outer class instance.

The non static member variables cannot be accessed by a class static method. The instance of a non static inner class cannot be created by a static class method. Both the method and the inner class should be modified as static or both should not be static. Otherwise, the exception No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ). will be thrown.

The inner class scope will be the same as the class member variable. The inner class can be declared as a static class as a static member variable. The instance of a non static inner class will be created with in the outer class object. The instance of the inner static class would be accessible at the class level. It can then be created in both static and not static methods.

Exception

The java error message will be seen as below in the eclipse.

No enclosing instance of type Test is accessible. Must qualify the allocation with an enclosing instance of type Test (e.g. x.new A() where x is an instance of Test).

The stack trace of the exception will be shown as shown below.

Exception in thread “main” java.lang.Error: Unresolved compilation problem: No enclosing instance of type SubListTest is accessible. Must qualify the allocation with an enclosing instance of type SubListTest (e.g. x.new A() where x is an instance of SubListTest). at com.yawintutor.SubListTest.load(SubListTest.java:10) at com.yawintutor.SubListTest.main(SubListTest.java:6)

Root Cause

Static methods can have access to either static variables or static methods. Static methods could not have access to non static variables or non static methods. Static methods are not allowed to have access to a non static inner class. An exception will be thrown if a static method attempts to create an instance of a non static inner class.

How to reproduce this exception

When the static method tries to create an instance of a non static inner class, the static method creates an exception. The static method would not be allowed to access the inner class that belongs to the outer class object. The example below reproduces the exception No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ).

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

Exception in thread “main” java.lang.Error: Unresolved compilation problem: No enclosing instance of type SubListTest is accessible. Must qualify the allocation with an enclosing instance of type SubListTest (e.g. x.new A() where x is an instance of SubListTest). at com.yawintutor.SubListTest.load(SubListTest.java:10) at com.yawintutor.SubListTest.main(SubListTest.java:6)

Solution 1

If the non static inner class is modified to the static inner class, the static method will provide access to the static inner class. Changing the non static to the static inner class would fix the exception.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } public static class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 2

If the static method is modified to a non static method, both the method and the inner class would be within the scope of the object. The non static method can be used to access the non static inner class. In this case, the instance of the outer class will be used.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { SubListTest subListTest = new SubListTest(); subListTest.load(); } public void load() { Department dept = new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 3

If the inner class is created outside the outer class or in another file, the inner class would be created as a separate class in the package. The class is going to be created like any other class. The exception will not be thrown.

SubListTest.java

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } }

Department.java

package com.yawintutor; public class Department { public String name=”dept”; public String getName() { return name; } }

Output

dept

Solution 4

When an instance of a class is created once in a static method, an instance of an outer class is created in a static method. The instance of the inner class can be created using the object of the outer class.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { SubListTest subListTest = new SubListTest(); Department dept = subListTest.new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 5

When an instance of a class is created once in a static method, an instance of an outer class is created in a static method. The instance of the inner class can be created using the object of the outer class. This is an another way of creating instance of the inner class using the local variable.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new SubListTest().new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

No enclosing instance of type is accessible – Yawin Tutor

The java No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ). exception happens when an instance is created for an inner class in the outer class static method. The static method attempts to create an object of an inner class that belongs to an outer class instance.

The non static member variables cannot be accessed by a class static method. The instance of a non static inner class cannot be created by a static class method. Both the method and the inner class should be modified as static or both should not be static. Otherwise, the exception No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ). will be thrown.

The inner class scope will be the same as the class member variable. The inner class can be declared as a static class as a static member variable. The instance of a non static inner class will be created with in the outer class object. The instance of the inner static class would be accessible at the class level. It can then be created in both static and not static methods.

Exception

The java error message will be seen as below in the eclipse.

No enclosing instance of type Test is accessible. Must qualify the allocation with an enclosing instance of type Test (e.g. x.new A() where x is an instance of Test).

The stack trace of the exception will be shown as shown below.

Exception in thread “main” java.lang.Error: Unresolved compilation problem: No enclosing instance of type SubListTest is accessible. Must qualify the allocation with an enclosing instance of type SubListTest (e.g. x.new A() where x is an instance of SubListTest). at com.yawintutor.SubListTest.load(SubListTest.java:10) at com.yawintutor.SubListTest.main(SubListTest.java:6)

Root Cause

Static methods can have access to either static variables or static methods. Static methods could not have access to non static variables or non static methods. Static methods are not allowed to have access to a non static inner class. An exception will be thrown if a static method attempts to create an instance of a non static inner class.

How to reproduce this exception

When the static method tries to create an instance of a non static inner class, the static method creates an exception. The static method would not be allowed to access the inner class that belongs to the outer class object. The example below reproduces the exception No enclosing instance of type is accessible. Must qualify the allocation with an enclosing instance of type (e.g. x.new A() where x is an instance of ).

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

Exception in thread “main” java.lang.Error: Unresolved compilation problem: No enclosing instance of type SubListTest is accessible. Must qualify the allocation with an enclosing instance of type SubListTest (e.g. x.new A() where x is an instance of SubListTest). at com.yawintutor.SubListTest.load(SubListTest.java:10) at com.yawintutor.SubListTest.main(SubListTest.java:6)

Solution 1

If the non static inner class is modified to the static inner class, the static method will provide access to the static inner class. Changing the non static to the static inner class would fix the exception.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } public static class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 2

If the static method is modified to a non static method, both the method and the inner class would be within the scope of the object. The non static method can be used to access the non static inner class. In this case, the instance of the outer class will be used.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { SubListTest subListTest = new SubListTest(); subListTest.load(); } public void load() { Department dept = new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 3

If the inner class is created outside the outer class or in another file, the inner class would be created as a separate class in the package. The class is going to be created like any other class. The exception will not be thrown.

SubListTest.java

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new Department(); System.out.println(dept.getName()); } }

Department.java

package com.yawintutor; public class Department { public String name=”dept”; public String getName() { return name; } }

Output

dept

Solution 4

When an instance of a class is created once in a static method, an instance of an outer class is created in a static method. The instance of the inner class can be created using the object of the outer class.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { SubListTest subListTest = new SubListTest(); Department dept = subListTest.new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

dept

Solution 5

When an instance of a class is created once in a static method, an instance of an outer class is created in a static method. The instance of the inner class can be created using the object of the outer class. This is an another way of creating instance of the inner class using the local variable.

package com.yawintutor; public class SubListTest { public static void main(String[] args) { load(); } public static void load() { Department dept = new SubListTest().new Department(); System.out.println(dept.getName()); } public class Department { public String name=”dept”; public String getName() { return name; } } }

Output

Error “is not an enclosing class”

I’m doing a Handler exercise just to test how it works, but I’m trying some problem I can not figure out.

This is my main class code:

public class MainActivity extends Activity { protected static final int MENSAGEM_TESTE = 1; private Handler handler = new TesteHandler(); Button button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = (Button) findViewById(R.id.button); button.setText(“Atualizar o texto em 3 segundos”); button.setOnClickListener(new Button.OnClickListener(){ @Override public void onClick(View view) { //Cria msg com delay de 3 seg Message msg = new Message(); msg.what = MENSAGEM_TESTE; //Envia msg handler.sendMessageDelayed(msg, 3000); } }); } }

And this is the code for my class TesteHandler :

import static com.exercicios.handler.MainActivity.MENSAGEM_TESTE; public class TesteHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case MENSAGEM_TESTE: Toast.makeText(MainActivity.this, “A mensagem chegou!”, Toast.LENGTH_SHORT).show(); break; } } }

Android Studio is returning me the following error:

‘com.exercicios.handler.MainActivity’ is not an enclosing class.

I’m not finding what I need to fix, can someone please give me a hand? Thank you in advance!

Java – Inner classes

Java – Inner classes

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In this chapter, we will discuss inner classes of Java.

Nested Classes

In Java, just like methods, variables of a class too can have another class as its member. Writing a class within another is allowed in Java. The class written within is called the nested class, and the class that holds the inner class is called the outer class.

Syntax

Following is the syntax to write a nested class. Here, the class Outer_Demo is the outer class and the class Inner_Demo is the nested class.

class Outer_Demo { class Inner_Demo { } }

Nested classes are divided into two types −

Non-static nested classes − These are the non-static members of a class.

Static nested classes − These are the static members of a class.

Inner Classes (Non-static Nested Classes)

Inner classes are a security mechanism in Java. We know a class cannot be associated with the access modifier private, but if we have the class as a member of other class, then the inner class can be made private. And this is also used to access the private members of a class.

Inner classes are of three types depending on how and where you define them. They are −

Inner Class

Method-local Inner Class

Anonymous Inner Class

Inner Class

Creating an inner class is quite simple. You just need to write a class within a class. Unlike a class, an inner class can be private and once you declare an inner class private, it cannot be accessed from an object outside the class.

Following is the program to create an inner class and access it. In the given example, we make the inner class private and access the class through a method.

Example

class Outer_Demo { int num; // inner class private class Inner_Demo { public void print() { System.out.println(“This is an inner class”); } } // Accessing he inner class from the method within void display_Inner() { Inner_Demo inner = new Inner_Demo(); inner.print(); } } public class My_class { public static void main(String args[]) { // Instantiating the outer class Outer_Demo outer = new Outer_Demo(); // Accessing the display_Inner() method. outer.display_Inner(); } }

Here you can observe that Outer_Demo is the outer class, Inner_Demo is the inner class, display_Inner() is the method inside which we are instantiating the inner class, and this method is invoked from the main method.

If you compile and execute the above program, you will get the following result −

Output

This is an inner class.

Accessing the Private Members

As mentioned earlier, inner classes are also used to access the private members of a class. Suppose, a class is having private members to access them. Write an inner class in it, return the private members from a method within the inner class, say, getValue(), and finally from another class (from which you want to access the private members) call the getValue() method of the inner class.

To instantiate the inner class, initially you have to instantiate the outer class. Thereafter, using the object of the outer class, following is the way in which you can instantiate the inner class.

Outer_Demo outer = new Outer_Demo(); Outer_Demo.Inner_Demo inner = outer.new Inner_Demo();

The following program shows how to access the private members of a class using inner class.

Example

class Outer_Demo { // private variable of the outer class private int num = 175; // inner class public class Inner_Demo { public int getNum() { System.out.println(“This is the getnum method of the inner class”); return num; } } } public class My_class2 { public static void main(String args[]) { // Instantiating the outer class Outer_Demo outer = new Outer_Demo(); // Instantiating the inner class Outer_Demo.Inner_Demo inner = outer.new Inner_Demo(); System.out.println(inner.getNum()); } }

If you compile and execute the above program, you will get the following result −

Output

This is the getnum method of the inner class: 175

Method-local Inner Class

In Java, we can write a class within a method and this will be a local type. Like local variables, the scope of the inner class is restricted within the method.

A method-local inner class can be instantiated only within the method where the inner class is defined. The following program shows how to use a method-local inner class.

Example

public class Outerclass { // instance method of the outer class void my_Method() { int num = 23; // method-local inner class class MethodInner_Demo { public void print() { System.out.println(“This is method inner class “+num); } } // end of inner class // Accessing the inner class MethodInner_Demo inner = new MethodInner_Demo(); inner.print(); } public static void main(String args[]) { Outerclass outer = new Outerclass(); outer.my_Method(); } }

If you compile and execute the above program, you will get the following result −

Output

This is method inner class 23

Anonymous Inner Class

An inner class declared without a class name is known as an anonymous inner class. In case of anonymous inner classes, we declare and instantiate them at the same time. Generally, they are used whenever you need to override the method of a class or an interface. The syntax of an anonymous inner class is as follows −

Syntax

AnonymousInner an_inner = new AnonymousInner() { public void my_method() { …….. …….. } };

The following program shows how to override the method of a class using anonymous inner class.

Example

abstract class AnonymousInner { public abstract void mymethod(); } public class Outer_class { public static void main(String args[]) { AnonymousInner inner = new AnonymousInner() { public void mymethod() { System.out.println(“This is an example of anonymous inner class”); } }; inner.mymethod(); } }

If you compile and execute the above program, you will get the following result −

Output

This is an example of anonymous inner class

In the same way, you can override the methods of the concrete class as well as the interface using an anonymous inner class.

Anonymous Inner Class as Argument

Generally, if a method accepts an object of an interface, an abstract class, or a concrete class, then we can implement the interface, extend the abstract class, and pass the object to the method. If it is a class, then we can directly pass it to the method.

But in all the three cases, you can pass an anonymous inner class to the method. Here is the syntax of passing an anonymous inner class as a method argument −

obj.my_Method(new My_Class() { public void Do() { ….. ….. } });

The following program shows how to pass an anonymous inner class as a method argument.

Example

// interface interface Message { String greet(); } public class My_class { // method which accepts the object of interface Message public void displayMessage(Message m) { System.out.println(m.greet() + “, This is an example of anonymous inner class as an argument”); } public static void main(String args[]) { // Instantiating the class My_class obj = new My_class(); // Passing an anonymous inner class as an argument obj.displayMessage(new Message() { public String greet() { return “Hello”; } }); } }

If you compile and execute the above program, it gives you the following result −

Output

Hello, This is an example of anonymous inner class as an argument

Static Nested Class

A static inner class is a nested class which is a static member of the outer class. It can be accessed without instantiating the outer class, using other static members. Just like static members, a static nested class does not have access to the instance variables and methods of the outer class. The syntax of static nested class is as follows −

Syntax

class MyOuter { static class Nested_Demo { } }

Instantiating a static nested class is a bit different from instantiating an inner class. The following program shows how to use a static nested class.

Example

public class Outer { static class Nested_Demo { public void my_method() { System.out.println(“This is my nested class”); } } public static void main(String args[]) { Outer.Nested_Demo nested = new Outer.Nested_Demo(); nested.my_method(); } }

If you compile and execute the above program, you will get the following result −

Output

This is my nested class

java – What causes error “No enclosing instance of type Foo is accessible” and how do I fix it?

You’ve declared the class Thing as a non-static inner class. That means it must be associated with an instance of the Hello class.

In your code, you’re trying to create an instance of Thing from a static context. That is what the compiler is complaining about.

There are a few possible solutions. Which solution to use depends on what you want to achieve.

Move Thing out of the Hello class.

Change Thing to be a static nested class. static class Thing

Create an instance of Hello before creating an instance of Thing . public static void main(String[] args) { Hello h = new Hello(); Thing thing1 = h.new Thing(); // hope this syntax is right, typing on the fly 😛 }

The last solution (a non-static nested class) would be mandatory if any instance of Thing depended on an instance of Hello to be meaningful. For example, if we had:

public class Hello { public int enormous; public Hello(int n) { enormous = n; } public class Thing { public int size; public Thing(int m) { if (m > enormous) size = enormous; else size = m; } } … }

any raw attempt to create an object of class Thing , as in:

Thing t = new Thing(31);

would be problematic, since there wouldn’t be an obvious enormous value to test 31 against it. An instance h of the Hello outer class is necessary to provide this h.enormous value:

… Hello h = new Hello(30); … Thing t = h.new Thing(31); …

Because it doesn’t mean a Thing if it doesn’t have a Hello .

For more information on nested/inner classes: Nested Classes (The Java Tutorials)

Java Error: No enclosing instance of type Main is accessible. Must qualify the allocation with an encl

The following error occurred today while compiling a Java program.

No enclosing instance of type Main is accessible. Must qualify the allocation with an enclosing instance of type Main (e.g. x.new A() where x is an instance of Main).

The source code I originally wrote looked like this

public class Main { class Dog { private String name; private int weight; public Dog(String name, int weight) { this.setName(name); this.weight = weight; } public int getWeight() { return weight; } public void setWeight(int weight) {this.weight = weight;} public void setName(String name) {this.name = name;} public String getName() {return name;} } public static void main(String[] args) { Dog d1 = new Dog(“dog1”,1); } }

When this error occurred, I didn’t quite understand it.

After learning from other people’s explanation, I suddenly realized.

In the code, my dog class is an internal class defined in main. The dog inner class is dynamic, while my main method is static.

Just as static methods cannot call dynamic methods.

There are two solutions:

Method 1

Define the inner class dog as a static class.

Method 2

Define the inner class dog outside the main class.

Read More:

No enclosing instance of type Foo is accessible

Java – No enclosing instance of type Foo is accessible

I have the following code: class Hello { class Thing { public int size; Thing() { size = 0; } } public static void main(String[] args) { Thing thing1 = new Thing(); System.out.println(“Hello, World!”); } } I know Thing does nothing, but my Hello, World program compiles just fine without it. It’s only my defined classes that are failing on me. And it refuses to compile. I get No enclosing instance of type Hello is accessible.” at the line that creates a new Thing. I’m guessing either: I have system level problems (either in DrJava or my Java install) or I have some basic misunderstanding of how to construct a working program in java. Any ideas?

static class Thing will make your program work. As it is, you’ve got Thing as an inner class, which (by definition) is associated with a particular instance of Hello (even if it never uses or refers to it), which means it’s an error to say new Thing(); without having a particular Hello instance in scope. If you declare it as a static class instead, then it’s a “nested” class, which doesn’t need a particular Hello instance.

You’ve declared the class Thing as a non-static inner class. That means it must be associated with an instance of the Hello class. In your code, you’re trying to create an instance of Thing from a static context. That is what the compiler is complaining about. There are a few possible solutions. Which solution to use depends on what you want to achieve. Move Thing out of the Hello class.

Change Thing to be a static nested class. static class Thing

Create an instance of Hello before creating an instance of Thing . public static void main(String[] args) { Hello h = new Hello(); Thing thing1 = h.new Thing(); // hope this syntax is right, typing on the fly 😛 } The last solution (a non-static nested class) would be mandatory if any instance of Thing depended on an instance of Hello to be meaningful. For example, if we had: public class Hello { public int enormous; public Hello(int n) { enormous = n; } public class Thing { public int size; public Thing(int m) { if (m > enormous) size = enormous; else size = m; } } … } any raw attempt to create an object of class Thing , as in: Thing t = new Thing(31); would be problematic, since there wouldn’t be an obvious enormous value to test 31 against it. An instance h of the Hello outer class is necessary to provide this h.enormous value: … Hello h = new Hello(30); … Thing t = h.new Thing(31); … Because it doesn’t mean a Thing if it doesn’t have a Hello . For more information on nested/inner classes: Nested Classes (The Java Tutorials)

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No enclosing instance of type Class is accessible

Sáng nay ngồi code chơi gặp tình huống thế này.

public class A { public class B{ private int num; public Date() { num = 0; } } public static void main(String[] args) { B b = new B(); } }

Dính ngay lỗi:

No enclosing instance of type A is accessible. Must qualify the allocation with an enclosing instance of type A(e.g. x.new B() where x is an instance of A)

Do lớp B là inner class của lớp A mà khi cần thì không thể truy xuất trực tiếp lớp B. Phải khi báo lớp A rồi hãy gọi B thông qua A.

Lý giải sâu hơn:

static class B will make your program work.

As it is, you’ve got B as an inner class, which (by definition) is associated with a particular instance of A (even if it never uses or refers to it), which means it’s an error to say new B(); without having a particular A instance in scope.

If you declare it as a static class instead, then it’s a “nested” class, which doesn’t need a particular A instance.

Giải quyết:

Cách 1:

A a = new A();

B b = a.new B();

Cách 2:

thêm từ khóa static lúc khai báo lớp B.

==> Thật là khó để tìm hiểu hết các vấn đề phải không bạn 🙂

Java mutation error: no enclosing instance of type XXX is accessible

Abstract ： Write java The following compilation error was encountered while code .

This article is shared from Huawei cloud community 《Java It appears that No enclosing instance of type XXX is accessible problem 》, author ：zhushy .

Error code and error phenomenon

Record the problem first , Write java The following compilation error was encountered while code .

No enclosing instance of type FileTree is accessible. Must qualify the allocation with an enclosing instance of type FileTree (e.g. x.new A() where x is an instance of FileTree).

The code is as follows ：

import java.util.Arrays; import java.util.LinkedHashMap; public class FileTree { class Node { String name; public Node(String name) { super(); this.name = name; } LinkedHashMap map = new LinkedHashMap(); } public static void outputThreeFormat(String[] in) { Arrays.sort(in); Node root = new Node(“/”); } public static void main(String[] args) { String[] in = { “usr/local/lib64”, “GAMES”, “usr/DRIVERS”, “home”, “var/log/” }; outputThreeFormat(in); } }

The error screenshot is as follows ：

How to solve these errors

The meaning of error is , There are no external instances that can be accessed enclosing instance. You must assign an appropriate external class FileTree Example （ Such as x.new A(),x Must be FileTree Example .）

Combine the wrong code , It’s easy to know what the root cause is ：

class Node It’s a non static inner class

and public static void outputThreeFormat(String[] in) It’s a static method

Static methods cannot directly access non static classes .

You can not use inner classes

You can put class Node Define as an external class , In this way FileTree Whether static or non static methods in a class can be used directly new Node Initialize nodes .

import java.util.Arrays; import java.util.LinkedHashMap; class Node { String name; public Node(String name) { super(); this.name = name; } LinkedHashMap map = new LinkedHashMap(); } public class FileTree { public static void outputThreeFormat(String[] in) { Arrays.sort(in); Node root = new Node(“/”); } public static void main(String[] args) { String[] in = { “usr/local/lib64”, “GAMES”, “usr/DRIVERS”, “home”, “var/log/” }; outputThreeFormat(in); } }

You can use static inner classes

You can put class Node As a static inner class definition , namely static class Node.

import java.util.Arrays; import java.util.LinkedHashMap; public class FileTree { static class Node { String name; public Node(String name) { super(); this.name = name; } LinkedHashMap map = new LinkedHashMap(); } public static void outputThreeFormat(String[] in) { Arrays.sort(in); Node root = new Node(“/”); } public static void main(String[] args) { String[] in = { “usr/local/lib64”, “GAMES”, “usr/DRIVERS”, “home”, “var/log/” }; outputThreeFormat(in); } }

When using non static inner classes , Call using an instance of an external class

As shown below .

import java.util.Arrays; import java.util.LinkedHashMap; public class FileTree { class Node { String name; public Node(String name) { super(); this.name = name; } LinkedHashMap map = new LinkedHashMap(); } public static void outputThreeFormat(String[] in) { Arrays.sort(in); FileTree ft=new FileTree(); Node root = ft.new Node(“/”); } public static void main(String[] args) { String[] in = { “usr/local/lib64”, “GAMES”, “usr/DRIVERS”, “home”, “var/log/” }; outputThreeFormat(in); } }

Query information , Learn more

Refer to online materials for in-depth study

• https://www.cnblogs.com/kungf… java Medium Static class

What’s the difference between static inner classes and non static inner classes ？ Here are the main differences between the two .

• （1） Internal static classes do not need to have references to external classes . But non static inner classes need to hold references to outer classes .

• （2） Non static inner classes can access static and non static members of outer classes . Static classes cannot access non static members of external classes . He can only access static members of external classes .

• （3） A non static inner class cannot be created without an outer class entity , A non static inner class can access the data and methods of the outer class , Because he’s in the outer class

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키워드에 대한 정보 no enclosing instance of type is accessible

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