10天轻松学习javase第5天上，Java 数组学习，完成对用户对象的增删改查
Java 数组是用来存储同类型元素的数据类型。
数组数组的申明：
数据类型 [] 数组名称 = new 数据类型[长度];
申明方式一
int data1[] = new int[3];
data1[0] = 10; // 第一个元素
data1[1] = 20; // 第二个元素
data1[2] = 30; // 第三个元素
申明方式二
int[] data2={10,20,30};
申明方式三
int[] data3=new int[]{10,20,30};
char类型数组；
char arr[] = new char[] {‘a’, ‘b’, ‘d’};
public static void main(String[] args) {
//int数组
int[] data=new int[]{10,20,30};
for (int i = 0; i < data.length; i++) {
System.out.println("data数组的第"+i+"个值："+data[i]);
}
}
Person per[] = new Person[3]; //动态初始化
per[0] = new Person(“张三”, 1);
per[1] = new Person(“王五”, 2);
per[2] = new Person(“李四”, 4);
public static void main(String[] args) {
//对象数组
Users user[] = new Users[3]; //动态初始化
user[0] = new Users(1,"admin","admin");
user[1] = new Users(2,"sili","123456");
}
//字符串数组
String[] weekarr={"星期天","星期一","星期二","星期三","星期四","星期五","星期六"};
Calendar calendar = Calendar.getInstance();
int num = calendar.get(Calendar.DAY_OF_WEEK) - 1;
String week = weekarr[num];
System.out.println(week);
对用户对象增删改查的例子
public class Users {
private int id;
private String name;
private String password;
public Users(int id, String name, String password) {
super();
this.id = id;
this.name = name;
this.password = password;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Override
public String toString() {
return "Users [id=" + id + ", name=" + name + ", password=" + password + "]";
}
}
import java.util.ArrayList;
import java.util.List;
public class UserAction {
private List<Users> userList =new ArrayList<Users>();
public Users add(Users users) {
if (users != null) {
Users u = new Users(users.getId(), users.getName(), users.getPassword());
this.userList.add(u);
}
return users;
}
public boolean delete(int id) {
List<Users> list = this.userList;
for (Users users : list) {
if (users.getId() == id) {
list.remove(id);
this.userList = list;
return true;
}
}
return false;
}
public Users selectOne(int id) {
List<Users> list = this.userList;
for (Users users : list) {
if (users.getId() == id) {
return users;
}
}
return null;
}
public List<Users> selectAll() {
return this.userList;
}
public Users update(Users users) {
List<Users> list = this.userList;
for (Users u : list) {
if (u.getId() == users.getId()) {
u.setName(users.getName());
u.setPassword(users.getPassword());
list.add(u.getId(), u);
}
}
return users;
}
}
import java.util.List;
public class UserActionDemo {
public static void main(String[] args) {
//对象数组
UserAction userAction =new UserAction();
Users user1 =new Users(1, "user1", "admin");
Users user2 =new Users(2, "user2", "admin");
Users user3 =new Users(3, "user3", "admin");
Users user4 =new Users(4, "user4", "admin");
Users user5 =new Users(5, "user5", "admin");
userAction.add(user1);
userAction.add(user2);
userAction.add(user3);
userAction.add(user4);
userAction.add(user5);
List<Users> reslist1 = userAction.selectAll();
System.out.println(reslist1);
userAction.delete(2);
List<Users> reslist2 = userAction.selectAll();
System.out.println(reslist2);
}
}
