Java入门与基础（工具包实例1list集合）

Posted 2021-06-19 晨沉宸辰

package test;
import java.util.ArrayList;
import java.util.List;//转化为数组所需
import java.util.Arrays;//转换为集合所需
public class listTest {
  public  static final List<Use> USERS=create();
  public static List<Use> create(){
	  Use user1= new Use("Bo");
	  Use user2= new Use("SUN");
	  Use user3= new Use("SUN");
	  List <Use> users=new ArrayList<>();
	  users.add(user1);
	  users.add(user2);
	  users.add(user3);
	  return users;
  }
  public static void main(String[] args) {
   	 //getsize();
   	//update();
 // update2();
  // 	update3();
	  //remove();
	  //ToArray();
	  ToArray1();
  }
  public static void getsize() {
	  System.out.println("这里开始计算长度——");
	  System.out.println(USERS.size());
	  System.out.println(USERS.isEmpty());
	  /*for(Use u:USERS) {
		  System.out.println(u.getName());
	  }*/
	  /*这里开始计算长度——
        3
        false*/
  }
  
  public static void update() {
	  System.out.println("这里开始学习储存方式——");
	  Use user4=USERS.get(0);
	  user4.setName("Zhang");
	  
	  for(Use u:USERS) {
		  System.out.println(u.getName());
	  }
	  /*这里开始学习储存方式——
Zhang
SUN
SUN*/
  }
  public static void update2() {
	  System.out.println("这里开始两次更新——");
	  Use user1=USERS.get(0);
	  Use user2=USERS.get(1);
	  for(Use u:USERS) {
		  u.setName("Zhang");
	  }
	  
	  
	  for(Use u:USERS) {
		  System.out.println(u.getName());}
	  /*这里开始计算长度——
         4
         false
         Bo
         SUN
         SUN
         Bo*/
  }
  
  public static void update3() {
	  System.out.println("这里开始取出第一个数然后加入判断大小以及排序——");
	  Use user1=USERS.get(0);
	 USERS.add(user1);
	getsize();
	  for(Use u:USERS) {
		  System.out.println(u.getName());
	  }
	  /*这里开始计算长度——
        4
        false
        Bo
        SUN
        SUN
        Bo*/
  }
  
 
  public static void remove() {
	  for(Use u:USERS) {
		  System.out.println(u.getName());
	  }
	  System.out.println("这里开始移除操作——");
	
	  for(Use u:USERS) {
		  if("SUN".contentEquals(u.getName()))
		 USERS.remove(u);
	  }
	  getsize();
	  for(Use u:USERS) {
		  System.out.println(u.getName());
	  }
	 /* Bo
	  SUN
	  SUN
	  这里开始移除操作——
	  这里开始计算长度——
	  2
	  false
	  Bo
	  SUN*/
	  }
	  
public static void ToArray() {
		 Use[] users = USERS.toArray(new Use[0]);
		 for(Use u:users) {
			  System.out.println(u.getName());
		  }
		/* Bo
		 SUN
		 SUN*/
	  }

public static void ToArray1() {
	 Use[] users = USERS.toArray(new Use[0]);
	List<Use> userlist = Arrays.asList(users);
	 for(Use u:userlist) {
		  System.out.println(u.getName());
	  } 
	/* Bo
	 SUN
	 SUN*/
 }
  

}

package test;

public class Use {
	public static final String HAERBIN ="哈";
	public static final String BEIJING ="北";
	private int id;
	private String name;
	private String city;
	public Use() {
		
	}
	public Use(String name) {
        this.name = name;
    }
    public Use(int id, String name, String city) {
        this.id = id;
        this.name = name;
        this.city = city;
    }
    public int getId() {
        return id;
    }

    public String getCity() {
        return city;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}