List、set以及map的遍历方式的整理

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/BinCain1993/article/details/78318889

@Test
public void foreachSet() {
    Set setObj = new HashSet();
    setObj.add("dsf");
    setObj.add(1);
    setObj.add(5);

    //first: iterator
    Iterator iterator = setObj.iterator();
    while (iterator.hasNext()) {
        System.out.println("set值: " + iterator.next());
    }

    //second: for(int i...)
    for (Object obj : setObj) {
        System.out.println("obj值: " + obj);
    }
}

@Test
public void foreachList() {
    List listObj = new ArrayList();
    listObj.add(1);
    listObj.add("88");

    //first:iterator
    Iterator iterator = listObj.iterator();
    while (iterator.hasNext()) {
        System.out.println(iterator.next());
    }
    //second:for(int i....)
    for (int i = 0; i < listObj.size(); i++) {
        System.out.println(listObj.get(i));
    }

    //third:foreach
    for (Object obj : listObj) {
        System.out.println(obj);
    }
}

@Test
public void foreachMap() {
    //first: 使用keySet遍历map
    Map<Integer, Integer> map = new HashMap<Integer, Integer>();
    map.put(1, 5);
    map.put(2, 6);
    map.put(3, 7);
    for (Integer keyInt : map.keySet()) {
        Integer valueInt = map.get(keyInt);
        System.out.println("key1 : " + keyInt + "  value1 : " + valueInt);
    }
    //second: 使用entrySet遍历map         
    Set<Map.Entry<Integer, Integer>> entrySet = map.entrySet();
    for (Map.Entry<Integer, Integer> entryObj : entrySet) {
        System.out.println("key2 : " + entryObj.getKey() + "  value2 : " + entryObj.getValue());
    }
    //third: 使用ITERATOR遍历map       
    Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
    while (entries.hasNext()) {
        Map.Entry<Integer, Integer> entry = entries.next();
        System.out.println("Key3 : " + entry.getKey() + "  Value3 : " + entry.getValue());
    }
}