Java 内部类

当生成一个内部类的对象时，此对象与制造它的外围对象就有了一种联系。所以其能访问
其外围对象的所有成员，而不需要任何特殊条件。此外，内部类还拥有其外围类的所有元素的
访问权。

在拥有外部类对象之前是不可能创建内部类对象的。这是因为内部类对象会暗暗地连接到它的外部类对象上。
但是，如果你创建时嵌套类（静态内部类），那么它就不需要对外部对象的引用。

public class DotThis {

	void f() {
		System.out.println("DotThis.f()");
	}
	
	public class Inner {
		public DotThis outer() {
			return DotThis.this;
		}
		
		public void say() {
			System.out.println("inner class");
		}
	}
	
	public Inner inner() {
		return new Inner();
	}
	
	public static void main(String[] args) {
		DotThis dotThis = new DotThis();
		DotThis.Inner inner = dotThis.inner();
		inner.outer().f();
		
		// 创建内部类对象
		DotThis.Inner dni = dotThis.new Inner();
		dni.say();
	}
}

public class Sequence {

	private Object[] items;
	private int next = 0;
	
	public Sequence(int size) {
		items = new Object[size];
	}
	
	public void add(Object x) {
		if (next < items.length) {
			items[next++] = x;
		}
	}
	
	private class SequenceSelector implements Selector {
		private int i = 0;
		@Override
		public boolean end() {
			return i == items.length;
		}

		@Override
		public Object current() {
			return items[i];
		}

		@Override
		public void next() {
			if (i < items.length) {
				i++;
			}
		}
		
	}
	
	public Selector selector() {
		return new SequenceSelector();
	}
	
	public static void main(String[] args) {
		Sequence sequence = new Sequence(10);
		for (int i=0; i<10; i++) {
			sequence.add(Integer.toString(i));
		}
		Selector selector  = sequence.selector();
		while (!selector.end()) {
			System.out.println(selector.current() + " ");
			selector.next();
		}
	}
	
}

public class Parcel4 {

	private class PContents implements Contents {
		private int i = 11;
		@Override
		public int value() {
			return i;
		}
	}
	protected class PDestination implements Destination {
		private String label;
		private PDestination(String whereTo) {
			this.label = whereTo;
		}
		@Override
		public String readLabel() {
			return label;
		}
	}
	
	public Destination destination(String s) {
		return new PDestination(s);
	}
	
	public Contents contents() {
		return new PContents();
	}
}

匿名内部类

public class Prac17 {

	public Contents contents() {
		return new Contents() {
			private int i = 11;
			@Override
			public int value() {
				return i;
			}
		};
	}
	public static void main(String[] args) {
		Prac17 prac17 = new Prac17();
		Contents c = prac17.contents();
	}
}