Java inner Classes (Member, local, anonymous)

Inner class format

public class Outer {
  public class Inner {
  }
}
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Inner class access features

An inner class can access members of an outer class directly, including private ones. To access members of an inner class, an outer class must create objects

Public class Outer {private int num = 10; Public class Inner {// Inner class method public void show() {system.out.println (num); Public void innerShow() {Inner I = new Inner(); i.show(); }}Copy the code

• Use inner classes in other classes

Inner i = new Outer().new Inner();
i.show();

Outer o = new Outer();
o.innerShow();
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Local inner class

A local inner class is a class defined in a method, so it cannot be used directly outside the method. You need to create objects and use them inside the method. The class can directly access the members of the external class, and can access local variables inside the method

Public class Outer {private int num = 10; Public void innerShow() {// Inner class Inner {// Inner class method public void show() {system.out.println (num); Inner I = new Inner(); i.show(); }}Copy the code

Anonymous inner class

Public class Outer {private int num = 10; Public void innerShow() {// New Inner() {// public void innerShow() {// system.out.println (num); // } // }.show(); Inner i = new Inner() { public void show() { System.out.println(num); }}; i.show(); }}Copy the code