Java-集合练习3

练习1  添加用户对象并判断是否存在

package com.lkbhua.Test;public class User {private String name;private int age;private String password;public User(){}public User(String name,int age,String password){this.name = name;this.age = age;this.password = password;}public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getPassword(){return password;}public void setPassword(String password){this.password = password;}
}

package com.lkbhua.Test;import java.util.ArrayList;public class ArrayListTest05 {public static void main(String[] args) {/*添加对象并判断是否存在*/// 1、创建ArrayList集合ArrayList<User> list = new ArrayList<>();// 2、创建三个用户对象User u1 = new User("张三", 18, "123456");User u2 = new User("曾琼", 22, "122136");User u3 = new User("王五", 19, "12qw56");// 3、添加用户对象list.add(u1);list.add(u2);list.add(u3);// 4、调用方法查询idboolean b = contains(list, "张三");System.out.println(b);}// 查询方法public static boolean contains(ArrayList<User>list, String id){for(int i = 0; i < list.size(); i++){// 利用list.get(i)获取集合中的元素// .getName()获取用户名// .equals()判断用户名是否相同// list.get(i).getName().equals(id);User u = list.get(i);String uid = u.getName();if(uid.equals(id)){return true;}}// 循环结束，没有找到return false;}
}

 

练习2  添加手机对象并返回要求的数据

package com.lkbhua.Test;public class Phone {private String brand;private double price;public Phone(){}public Phone(String brand,double price){this.brand = brand;this.price = price;}public String getBrand(){return brand;}public void setBrand(String brand){this.brand = brand;}public double getPrice(){return price;}public void setPrice(double price){this.price = price;}
}

package com.lkbhua.Test;import java.util.ArrayList;public class ArrayListTest06 {public static void main(String[] args) {/*添加手机对象并按要求返回数据*/// 1、创建ArrayListArrayList<Phone> list = new ArrayList<>();// 2、创建手机对象Phone p1 = new Phone("Apple17", 8888);Phone p2 = new Phone("HuaweiMate80", 6666);Phone p3 = new Phone("Xiaomi17pro", 5555);Phone p4 = new Phone("Vivos19", 2444);Phone p5 = new Phone("OppoReno13", 2033);Phone p6 = new Phone("OppoA5", 2222);Phone p7 = new Phone("OnePlus", 1111);// 3、添加手机对象list.add(p1);list.add(p2);list.add(p3);list.add(p4);list.add(p5);list.add(p6);list.add(p7);// 4、调用方法printArrayList(list);// 5、接受ArrayList<Phone> phoneInfoList = getPhone(list);// 遍历for(int i = 0; i < phoneInfoList.size(); i++){Phone p = phoneInfoList.get(i);System.out.println(p.getBrand() + "---" + p.getPrice());}}// case1：打印的方法public static void printArrayList(ArrayList<Phone> list){for(int i = 0; i < list.size(); i++){Phone p = list.get(i);double price = p.getPrice();if(price < 3000){System.out.println(p.getBrand() + "---" + p.getPrice());}}}// case2：返回手机对象// 技巧：// 如果以后要返回多个数据，可以把这些数据放到一个容器当中，再把容器返回// 可以是集合、数组public static ArrayList<Phone> getPhone(ArrayList<Phone> list){// 定义一个集合用以存储并返回低于3000的手机对象ArrayList<Phone> resultList = new ArrayList<>();for(int i = 0; i < list.size(); i++){Phone p = list.get(i);double price = p.getPrice();if(price < 3000){resultList.add(p);}}return resultList;}
}

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