java中迭代器的原理图解和源码浅析

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public interface Inteator {
    public abstract boolean hasNext(); // 注意：默认方法前有public abstract修饰，是接口中方法的默认修饰符
    public abstract Object next();     // 注意：默认方法前有public abstract修饰，是接口中方法的默认修饰符
}

public interface Iterable {
    Iterator iterator(); // 没有具体实现，注意：默认方法前有public abstract修饰，是接口中方法的默认修饰符
}
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public interface Collection extends Iterable {
    Iterator iterator(); // 没有具体实现，注意：默认方法前有public abstract修饰，是接口中方法的默认修饰符
}

public interface List extends Collection {
    Iterator iterator(); // 没有具体实现，注意：默认方法前有public abstract修饰，是接口中方法的默认修饰符
}
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public class ArrayList implements List {
    public Iterator iterator() { // 具体实现
        return new Itr();
    }
    
    private class Itr implements Iterator { // Itr是Iterator接口的实现类
        public boolean hasNext() {}
        public Object next(){} 
    }
}
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Collection c = new ArrayList();
c.add("hello");
c.add("world");
c.add("java");
Iterator it = c.iterator();     // new Itr();
while(it.hasNext()) {
    String s = (String)it.next();
    System.out.println(s);
}
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