学习Java33天（练习）

import java.util.ArrayList; public class ArrayListDemo3 { public static void main(String[] args) { //1.创建集合 ArrayList<String> list = new ArrayList<>(); //2.添加元素 list.add("元素1"); list.add("元素2"); list.add("元素3"); //3.遍历 System.out.print("["); for (int i = 0; i < list.size(); i++) { if (i== list.size()-1){ System.out.print(list.get(i)+"]"); }else { System.out.print(list.get(i)+","); } } } }

import java.util.ArrayList; public class ArrayListDemo4 { public static void main(String[] args) { ArrayList<Integer> list = new ArrayList<>(); list.add(10); list.add(20); list.add(30); ArrayList<Character> list1 = new ArrayList<>(); list1.add('a'); list1.add('b'); list1.add('c'); System.out.print("["); for (int i = 0; i < list.size(); i++) { if (i == list.size()-1){ System.out.print(list.get(i)+"]"); }else{ System.out.print(list.get(i)+","); } } System.out.println(); System.out.print("["); for (int i = 0; i < list1.size(); i++) { if (i == list1.size()-1){ System.out.print(list1.get(i)+"]"); }else{ System.out.print(list1.get(i)+","); } } } }

import java.util.ArrayList; import java.util.Scanner; public class Student1Test { public static void main(String[] args) { ArrayList<Student1> list = new ArrayList<>(); Scanner Sc = new Scanner(System.in); //Student1 s1 = new Student1("张三",18); //Student1 s2 = new Student1("李四",19); //Student1 s3 = new Student1("王五",20); //list.add(s1); //list.add(s2); //list.add(s3); for (int i = 0; i < 3; i++) { Student1 stu = new Student1(); System.out.println("请输入学生的姓名："); String name = Sc.next(); System.out.println("请输入学生的年龄："); int age = Sc.nextInt(); stu.setName(name); stu.setAge(age); list.add(stu); } for (int i = 0; i < list.size(); i++) { Student1 s = list.get(i); System.out.println(s.getName()+","+s.getAge()); } } } public class Student1 { private String name ; private int age; public Student1(){} public Student1(String name,int age){ this.name = name; this.age = age; } public String getName(){ return name; } public int getAge() { return age; } public void setName(String name) { this.name = name; } public void setAge(int age) { this.age = age; } }

import java.util.ArrayList; public class UserText { public static void main(String[] args) { ArrayList<User> list = new ArrayList<>(); User u1 = new User("001","张三","00123"); User u2 = new User("002","李四","00223"); User u3 = new User("003","王五","00323"); list.add(u1); list.add(u2); list.add(u3); boolean flag = contains(list,"5"); int index = getIndex(list,"005"); System.out.println(flag); System.out.println(index); } public static boolean contains(ArrayList<User> list,String id){ for (int i = 0; i < list.size(); i++) { User u = list.get(i); String uid = u.getId(); if (uid.equals(id)){ return true; } } return false; } public static int getIndex(ArrayList<User> list,String id){ for (int i = 0; i < list.size(); i++) { User u = list.get(i); String uid = u.getId(); if (uid.equals(id)){ return i; } } return -1; } } 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; } public String getId(){ return id; } public void setId(String id) { this.id = id; } public String getUsername(){ return username; } public void setUsername(String username) { this.username = username; } public String getPassword(){ return password; } public void setPassword(String password){ this.password = password; } }

import java.util.ArrayList; public class Phone1Text { public static void main(String[] args) { ArrayList<Phone1> list = new ArrayList<>(); Phone1 p1 = new Phone1("小米",1000); Phone1 p2 = new Phone1("华为",8000); Phone1 p3 = new Phone1("锤子",2999); list.add(p1); list.add(p2); list.add(p3); ArrayList<Phone1> phoneInfo = getPhoneInfo(list); for (int i = 0; i < phoneInfo.size(); i++) { Phone1 phone1 = phoneInfo.get(i); System.out.println(phone1.getBrand()+","+phone1.getPrice()); } } public static ArrayList<Phone1> getPhoneInfo(ArrayList<Phone1> list){ ArrayList<Phone1> result = new ArrayList<>(); for (int i = 0; i < list.size(); i++) { Phone1 P = list.get(i); int price = P.getPrice(); if (price< 3000) { result.add(P); } } return result; } } public class Phone1 { private String brand; private int price; public Phone1(){} public Phone1(String brand,int price){ this.brand = brand; this.price = price; } public String getBrand(){ return brand; } public void setBrand(String brand){ this.brand = brand; } public int getPrice(){ return price; } public void setPrice(int price){ this.price = price; } }