java——Map集合遍历
一、Map集合遍历的三种方法:
1)Set<K> keySet();
2)Collection<V> values();
3)Set<Map.Entry<K,V>> entrySet();
二、Set<K> keySet();
1)把Map中所有的键名传入到set集合;
2)用set集合中的迭代器取出所有键名;
3)通过键名从map中获得键值;
public class Test { public static void main(String[] args) { HashMap<String, String> map = new HashMap<>(); map.put("1", "zs"); map.put("1", "zs"); map.put("2", "ls"); Set<String> set = map.keySet(); for (Iterator<String> iterator = set.iterator(); iterator.hasNext(); ) { String key = iterator.next(); System.out.println(key); String value = map.get(key); System.out.println(value); } } }
三、Collection<V> values();
1)通过values方法直接获取所有键值;
2)迭代器遍历键值;
public class Test { public static void main(String[] args) { HashMap<String, String> map = new HashMap<>(); map.put("1", "zs"); map.put("1", "zs"); map.put("2", "ls"); Collection<String> values = map.values(); for (Iterator<String> iterator = values.iterator(); iterator.hasNext(); ) { String value = iterator.next(); System.out.println(value); } } }
四、Set<Map.Entry<K,V>> entrySet();
1)通过entrySet方法,把map集合的键值对存入set集合;
2)遍历set集合,通过get方法获取键名键值;
public class Test { public static void main(String[] args) { HashMap<String, String> map = new HashMap<>(); map.put("1", "zs"); map.put("1", "zs"); map.put("2", "ls"); Set<Map.Entry<String, String>> entries = map.entrySet(); for (Iterator<Map.Entry<String, String>> iterator = entries.iterator(); iterator.hasNext(); ) { Map.Entry<String, String> entry = iterator.next(); System.out.println(entry.getKey()); System.out.println(entry.getValue()); } } }