存入三个用户对象,根据id查找用户信息1.存在则返回true 2.存在则返回该用户(索引)
package com.itheima.test; //创建个User类 public class User { private String id; private String username; private String password; public User() { } public User(String id, String username, String password) { this.id = id; this.username = username; this.password = password; } /** * 获取 * @return id */ public String getId() { return id; } /** * 设置 * @param id */ public void setId(String id) { this.id = id; } /** * 获取 * @return username */ public String getUsername() { return username; } /** * 设置 * @param username */ public void setUsername(String username) { this.username = username; } /** * 获取 * @return password */ public String getPassword() { return password; } /** * 设置 * @param password */ public void setPassword(String password) { this.password = password; } public String toString() { return "User{id = " + id + ", username = " + username + ", password = " + password + "}"; } }
package com.itheima.test; import java.util.ArrayList; public class Test6 { public static void main(String[] args) { ArrayList<User> list = new ArrayList<>(); //创建用户对象 User user = new User("00001","张","11111"); User user1 = new User("00002","王","11111"); User user2 = new User("00003","王","11111"); //将用于对象添加至集合 list.add(user); list.add(user1); list.add(user2); //调用方法 boolean flag = SelectInfoFromUserId(list, "00001"); //打印结果 System.out.println(flag); } //需要信息和id 信息是集合ArrayList<User> list public static boolean SelectInfoFromUserId(ArrayList<User> list,String id){ for (int i = 0; i < list.size(); i++) { //i是集合里的用户对象 //list.get(i).getId().equals(id); //先list.get 再getid User user = list.get(i); String uid= user.getId(); if(uid.equals(id)){ return true; } } return false; } }
package com.itheima.test; import java.util.ArrayList; public class Test6test3 { public static void main(String[] args) { //1.定义集合 ArrayList<User> list = new ArrayList<>(); //2.定义用户 User user = new User("0001","zhang","mima1"); User user1 = new User("0002","wang","mima2"); User user2 = new User("0003","li","mima3"); //3.添加 list.add(user); list.add(user1); list.add(user2); //4.调用 int index = getIndex(list, "0001"); System.out.println(index); } public static int getIndex(ArrayList <User> list,String id) { for (int i = 0; i < list.size(); i++) { //获取数组中的id //list.get(i).getId().equals(id); User user = list.get(i); //获取 String uid = user.getId(); //比较 if(uid.equals(id)){ return i; } } return -1; } }
//既返回方法, 又判断 //boolean方法不写,直接返回 return getIndex(list,id)>=0;
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