Map的5种遍历方法

2023-03-16 15:25:07 浏览数 (1)

代码语言:javascript复制
//循环遍历map的方法
public class MapF {
         public static void main(String[] args) {

          Map<String, Integer> tempMap = new HashMap<String, Integer>();
          tempMap.put("a","12");
          tempMap.put("b","34");
          tempMap.put("c","56");

          // JDK1.4中
          // 遍历方法一 hashmap entrySet() 遍历
          Iterator it = tempMap.entrySet().iterator();
          while (it.hasNext()) {
           Map.Entry entry = (Map.Entry) it.next();
           Object key = entry.getKey();
           Object value = entry.getValue();
           System.out.println("key="   key   " value="   value);
          }
          System.out.println("");

          // JDK1.5中,应用新特性For-Each循环
          // 遍历方法二
          for (Map.Entry<String, Integer> entry : tempMap.entrySet()) {
           String key = entry.getKey().toString();
           String value = entry.getValue().toString();
           System.out.println("key="   key   " value="   value);
          }
          System.out.println("");

          // 遍历方法三 hashmap keySet() 遍历
          for (Iterator i = tempMap.keySet().iterator(); i.hasNext();) {
           Object obj = i.next();
           System.out.println(obj);// 循环输出key
           System.out.println("key="   obj   " value="   tempMap.get(obj));
          }
          for (Iterator i = tempMap.values().iterator(); i.hasNext();) {
           Object obj = i.next();
           System.out.println(obj);// 循环输出value
          }

          // 遍历方法四 treemap keySet()遍历
          for (Object o : tempMap.keySet()) {
           System.out.println("key="   o   " value="   tempMap.get(o));
          }
          System.out.println("11111");
          // java如何遍历Map <String, ArrayList> map = new HashMap <String,
          // ArrayList>();
          System.out.println("java  遍历Map <String, ArrayList> map = new HashMap<String, ArrayList>();");
          Map<String, ArrayList> map = new HashMap<String, ArrayList>();
          Set<String> keys = map.keySet();
          Iterator<String> iterator = keys.iterator();
          while (iterator.hasNext()) {
           String key = iterator.next();
           ArrayList arrayList = map.get(key);
           for (Object o : arrayList) {
            System.out.println(o);
           }
          }

          Map<String, List> map = new HashMap<String, List>();
          for (Map.Entry entry : map.entrySet()) {
           String key = entry.getKey().toString();
           List<String> list= (List) entry.getValue();
           for (String value : list) {
            System.out.println(key   "===="   value);
           }
          }
         }
}

0 人点赞