Iterator概述

玩具代码案例 - 字符串的迭代器

String默认是不支持迭代器的，即也不能支持 for each的语法。这里通过一个StringIterable来封装一个支持迭代器的字符串，实现了Iterable接口的类就能支持for each

迭代器类型

StringIterable

package online.javabook.gof.behavioral.patterns3.iterator.characters;
import java.util.Iterator;
public class StringIterable implements Iterable<Character> {
    private String original;
    public StringIterable(String original) {
        this.original = original;
    }
    public Iterator<Character> iterator() {
        return new InnerIterator();
    }
    // InnerIterator
    private class InnerIterator implements Iterator<Character> {
        private int index;
        public boolean hasNext() {
            return index < original.length();
        }
        public Character next() {
            Character c = original.charAt(index);
            index++;
            return c;
        }
        public void remove() {}
    }
}

控制台输出

Main

package online.javabook.gof.behavioral.patterns3.iterator.characters.app;
import online.javabook.gof.behavioral.patterns3.iterator.characters.StringIterable;
import java.util.Iterator;
public class Main {
    public static void main(String[] args) {
        StringIterable iterable = new StringIterable("abcdef");
        Iterator<Character> iterator = iterable.iterator();
        while(iterator.hasNext()) {
            System.out.println(iterator.next());
        }
        System.out.println("----------------------------------------");
        for(Character character : iterable) {
            System.out.println(character);
        }
    }
}

Console

a
b
c
d
e
f
----------------------------------------
a
b
c
d
e
f