list和map是java集合中的必备类,当然他们的遍历也是至关重要的。
list的遍历:
1.for循环
for (Integer each : list) { System.out.println(each); }
2.iterator循环
Iterator<Integer> iterator = list.iterator(); while (iterator.hasNext()) { System.out.println(iterator.next()); }
3.正规的for循环
for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); }
整个demo如下:
List<Integer> list = new ArrayList<Integer>(); list.add(1); list.add(2); list.add(3); System.out.println("第一种方式:精简的for循环---------------"); for (Integer each : list) { System.out.println(each); } System.out.println(); System.out.println("第二种方式:iterator指针---------------"); Iterator<Integer> iterator = list.iterator(); while (iterator.hasNext()) { System.out.println(iterator.next()); } System.out.println(); System.out.println("第三种方式:正常的for循环---------------"); for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); } System.out.println();
map的遍历:
使用entrySet()方法遍历:
for (Entry<String, String> each : map.entrySet()) { System.out.println(each.getKey() + ":" + each.getValue()); }
demo如下:
Map<String, String> map = new HashMap<String, String>(); map.put("1", "小王"); map.put("2", "小李"); map.put("3", "小黑"); for (Entry<String, String> each : map.entrySet()) { System.out.println(each.getKey() + ":" + each.getValue()); }