Local Inner class in Java

by Online Tutorials Library July 22, 2022

Java Local inner class

A class i.e., created inside a method, is called local inner class in java. Local Inner Classes are the inner classes that are defined inside a block. Generally, this block is a method body. Sometimes this block can be a for loop, or an if clause. Local Inner classes are not a member of any enclosing classes. They belong to the block they are defined within, due to which local inner classes cannot have any access modifiers associated with them. However, they can be marked as final or abstract. These classes have access to the fields of the class enclosing it.

If you want to invoke the methods of the local inner class, you must instantiate this class inside the method.

Java local inner class example

LocalInner1.java

  public class localInner1{   private int data=30;//instance variable   void display(){    class Local{     void msg(){System.out.println(data);}    }    Local l=new Local();    l.msg();   }   public static void main(String args[]){    localInner1 obj=new localInner1();    obj.display();   }  }  

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Output:

Internal class generated by the compiler

In such a case, the compiler creates a class named Simple$1Local that has the reference of the outer class.

  import java.io.PrintStream;  class localInner1$Local  {      final localInner1 this$0;      localInner1$Local()      {             super();          this$0 = Simple.this;      }      void msg()      {          System.out.println(localInner1.access$000(localInner1.this));      }  }  

Rule: Local variables can’t be private, public, or protected.

Rules for Java Local Inner class

1) Local inner class cannot be invoked from outside the method.

2) Local inner class cannot access non-final local variable till JDK 1.7. Since JDK 1.8, it is possible to access the non-final local variable in the local inner class.

Example of local inner class with local variable

LocalInner2.java

  class localInner2{   private int data=30;//instance variable   void display(){    int value=50;//local variable must be final till jdk 1.7 only    class Local{     void msg(){System.out.println(value);}    }    Local l=new Local();    l.msg();   }   public static void main(String args[]){    localInner2 obj=new localInner2();    obj.display();   }  }  

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Output:

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