Java 集合List Set Map 循環的遍歷 EnumMap集合的操作

2019-11-14 08:55:07

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1：List集合遍歷的方式（ArrayList為例） 1.1 實體類 public class User { PRivate String username; private String address; private int age;

public User() { super();}public User(String username, String address, int age) { super(); this.username = username; this.address = address; this.age = age;}public String getUsername() { return username;}public void setUsername(String username) { this.username = username;}public String getAddress() { return address;}public void setAddress(String address) { this.address = address;}public int getAge() { return age;}public void setAge(int age) { this.age = age;}@Overridepublic String toString() { return "User [username=" + username + ", address=" + address + ", age=" + age + "]";}

} 1.2向集合中添加User對象 List list=new ArrayList<>();

List<User> list1=new ArrayList<>(); User user1=new User("劉備","今河北省保定市涿州市",1800); User user2=new User("張飛","河北",1800); User user3=new User("關羽","山西解梁",1800); User user4=new User("趙云","河北常山",1800); User user5=new User("諸葛亮","河南南陽",1800); list.add(user1); list.add(user2); list.add(user3); list.add(user4); list.add(user5); System.out.println("list集合foreach循環"); for (User user : list) { if(user.getUsername().equals("劉備")){ user.setAddress("搬遷到四川成都成為蜀國的君王"); } System.out.println("姓名："+user.getUsername()+",戶籍："+user.getAddress()+ ",年齡："+user.getAge()); } System.out.println("list集合for循環"); for(int i=0;i<list.size();i++){ System.out.println("姓名："+list.get(i).getUsername()+",戶籍："+list.get(i).getAddress()+ ",年齡："+list.get(i).getAge()); } System.out.println("list集合Iterator"); if(list1.isEmpty()){ System.out.println("list1集合為空"); } Iterator<User> it=list1.iterator(); while(it.hasNext()){ System.out.println(it.next()); } System.out.println("list集合Lamda循環"); list.forEach(l->System.out.println(l));

2：Set集合的遍歷（HashSet為例，不能使用for循環遍歷） Set set = new HashSet<>(); User user1 = new User(“劉備”, “今河北省保定市涿州市”, 1800); User user2 = new User(“張飛”, “河北”, 1800); User user3 = new User(“關羽”, “山西解梁”, 1800); User user4 = new User(“趙云”, “河北常山”, 1800); User user5 = new User(“諸葛亮”, “河南南陽”, 1800); set.add(user1); set.add(user2); set.add(user3); set.add(user4); set.add(user5); System.out.println(“set集合foreach循環”); for (User user : set) { if (user.getUsername().equals(“劉備”)) { user.setAddress(“搬遷到四川成都成為蜀國的君王”); } System.out.println(“姓名：” + user.getUsername() + “,戶籍：” + user.getAddress() + “,年齡：” + user.getAge()); } System.out.println(“set集合Iterator”); if (set.isEmpty()) { System.out.println(“set1集合為空”); } Iterator it = set.iterator(); while (it.hasNext()) { System.out.println(it.next()); } System.out.println(“set集合Lamda循環”); set.forEach(l -> System.out.println(l)); 3：Map集合的遍歷（HashMap為例） Map

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