第一种,将map中的key存储在Set集合中:
(1)iterator:
Map<String, Integer> map = new HashMap<>(); map.put("a", 1); map.put("b", 2); map.put("c", 3); //Integer i = map.get("a"); //System.out.println(i); Set<String> keySet = map.keySet();//获取key集合 Iterator<String> it = keySet.iterator(); while (it.hasNext()) { String s = it.next(); Integer i = map.get(s); System.out.println(s+" "+i); }
(2)foreach:
Map<String, Integer> map = new HashMap<>(); map.put("a", 1); map.put("b", 2); map.put("c", 3); for(String key : map.keySet()) { System.out.println(key+":"+map.get(key)); }
第二种:使用map.entrySet()将map中的key-value转换成对象存储在Set<Map.entrySet<k,v>>中
(1)iterator
Map<String, Integer> map = new HashMap<>(); map.put("a", 1); map.put("b", 2); map.put("c", 3); Set<Map.Entry<String, Integer>> entrySet = map.entrySet(); Iterator<Map.Entry<String, Integer>> it = entrySet.iterator(); while (it.hasNext()) { Map.Entry<String, Integer> en = it.next(); String key = en.getKey(); Integer value = en.getValue(); System.out.println(key+" "+value); }
(2)foreach
Map<String, Integer> map = new HashMap<>(); map.put("a", 1); map.put("b", 2); map.put("c", 3); for(Map.Entry<String, Integer> en : map.entrySet() ) { String key = en.getKey(); Integer value = en.getValue(); System.out.println(key+" "+value); }