Map

package com.iterator.demo;

import java.util.HashMap;
import java.util.Map;

public class IteratorDemo {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<String, Integer>();
        map.put("", 1);
        map.put("two", 2);
        map.put(null, 3);
        System.out.println(map.put("two", 4));//key重复
        System.out.println(map.put("five", 5));
    }
}

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