HashMap的遍历

键找值：键相同，值覆盖；

//Map 集合的遍历 HashMap<String, String> map = new HashMap<>(); String s = map.put("S001", "PGONE"); //第一次存储返回值是null String s1 = map.put("S001", "LULU"); //再次存储相同的键，新的值，会覆盖旧值，返回旧值 map.put("陈羽凡", "白百合"); map.put("陈思成", "佟丽娅"); map.put("武大", "金莲"); //获取所有得键得集合 Set<String> keySet = map.keySet(); for (String key : keySet) { //键找值 String value = map.get(key); System.out.println(key+"===="+value); }

键值对

HashMap<String, String> map = new HashMap<>(); String s = map.put("文章", "马伊琍"); //第一次存储返回值是null String s1 = map.put("文章", "姚笛"); //再次存储相同的键，新的值，会覆盖旧值，返回旧值 map.put("陈羽凡", "白百合"); map.put("陈思成", "佟丽娅"); map.put("武大", "金莲"); //获取键值对对象Entry,把键值统一看作一个整体 Set<Map.Entry<String, String>> entries = map.entrySet(); // Entry 键值对 //getKey ():返回与此项对应的键。 //getValue():返回与此项对应的值。 for (Map.Entry<String, String> entry : entries) { String key = entry.getKey(); String value = entry.getValue(); System.out.println(key+"====="+value); } HashMap<Student, String> map = new HashMap<>(); Student s1 = new Student("张三", 28); map.put(s1, "s001");//传入键值，此集合不能自动排序 map.put(new Student("李四", 24), "s002"); map.put(new Student("王五", 25), "s003"); map.put(new Student("赵六", 26), "s004"); map.put(new Student("张三", 23), "s005"); //遍历方式1：键找值 Set<Student> students = map.keySet(); for (Student key : students) { String value = map.get(key); System.out.println(key.getName()+"=="+key.getAge()+"========="+value); } System.out.println("========================"); //遍历方式1：键值对 Set<Map.Entry<Student, String>> entries = map.entrySet(); for (Map.Entry<Student, String> entry : entries) { Student key = entry.getKey(); String value = entry.getValue(); System.out.println(key.getName() + "==" + key.getAge() + "=========" + value); } Collection<String> values = map.values();//获得hashmap集合的值 System.out.println(values);//打印值