在 Java 中有 4 种不同类型的内部类可以使用. 下面给出它们的名称和例子.
1. 静态嵌套类 (Static Nested Classes)
class Outer { static class Inner { void go() { System.out.println("Inner class reference is:" + this); } }} public class Test { public static void main(String[] args) { Outer.Inner n = new Outer.Inner(); n.go(); }}
输出: Inner class reference is: Outer$Inner@19e7ce87
2. 成员内部类 (Member Inner Class)
成员类是特定于实例的. 它可以访问所有方法, 字段和外部类本身的引用.
public class Outer { private int x = 100; public void makeInner(){ Inner in = new Inner(); in.seeOuter(); } class Inner{ public void seeOuter(){ System.out.println("Outer x is" + x); System.out.println("Inner class reference is" + this); System.out.println("Outer class reference is" + Outer.this); } } public static void main(String [] args){ Outer o = new Outer(); Inner i = o.new Inner(); i.seeOuter(); }}
输出:
- Outer x is 100
- Inner class reference is Outer$Inner@4dfd9726
- Outer class reference is Outer@43ce67ca
3. 局部方法内部类 (Method-Local Inner Classes)
public class Outer { private String x = "outer"; public void doStuff() { class MyInner { public void seeOuter() { System.out.println("x is" + x); } } MyInner i = new MyInner(); i.seeOuter(); } public static void main(String[] args) { Outer o = new Outer(); o.doStuff(); }}
输出: x is outer
public class Outer { private static String x = "static outer"; public static void doStuff() { class MyInner { public void seeOuter() { System.out.println("x is" + x); } } MyInner i = new MyInner(); i.seeOuter(); } public static void main(String[] args) { Outer.doStuff(); }}
输出: x is static outer
4. 匿名内部类 (Anonymous Inner Classes)
当您需要给一个 GUI 应用程序窗口小部件加一个动作监听器时, 匿名内部类就会经常被用到.
button.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){ comp.setText("Button has been clicked"); }});
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来源: http://www.jianshu.com/p/aac79187033d