「Java」Collections.reverse()メソットでListに格納Beanクラスの要素の順序を逆にする
構文
List<クラス名>リスト名=new ArrayList<クラス名>();
使用例
1.JavaBeanクラスの定義
package com.arkgame.java.study;
public class UserData {
private String username;
private String pwd;
public UserData() {
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
package com.arkgame.java.study;
public class UserData {
private String username;
private String pwd;
public UserData() {
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
package com.arkgame.java.study; public class UserData { private String username; private String pwd; public UserData() { } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPwd() { return pwd; } public void setPwd(String pwd) { this.pwd = pwd; } }
2.Collections.reverse()でリストのBean要素を逆にする
package com.arkgame.java.study;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class CollectionRerveDemo {
public static void main(String[] args) {
List<UserData> cftLst = new ArrayList<UserData>();
// クラスのオブジェクト初期設定
UserData user1 = new UserData();
UserData user2 = new UserData();
UserData user3 = new UserData();
user1.setUsername("TestUser_01");
user1.setPwd("110");
// リストにオブジェクトの追加
cftLst.add(user1);
user2.setUsername("TestUser_02");
user2.setPwd("222");
cftLst.add(user2);
user3.setUsername("TestUser_03");
user3.setPwd("333");
cftLst.add(user3);
System.out.println("リストの要素(reverse before)");
for (UserData userData : cftLst) {
System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd());
}
Collections.reverse(cftLst);
System.out.println("リストの要素(reverse after)");
for (UserData userData : cftLst) {
System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd());
}
}
}
package com.arkgame.java.study;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class CollectionRerveDemo {
public static void main(String[] args) {
List<UserData> cftLst = new ArrayList<UserData>();
// クラスのオブジェクト初期設定
UserData user1 = new UserData();
UserData user2 = new UserData();
UserData user3 = new UserData();
user1.setUsername("TestUser_01");
user1.setPwd("110");
// リストにオブジェクトの追加
cftLst.add(user1);
user2.setUsername("TestUser_02");
user2.setPwd("222");
cftLst.add(user2);
user3.setUsername("TestUser_03");
user3.setPwd("333");
cftLst.add(user3);
System.out.println("リストの要素(reverse before)");
for (UserData userData : cftLst) {
System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd());
}
Collections.reverse(cftLst);
System.out.println("リストの要素(reverse after)");
for (UserData userData : cftLst) {
System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd());
}
}
}
package com.arkgame.java.study; import java.util.ArrayList; import java.util.Collections; import java.util.List; public class CollectionRerveDemo { public static void main(String[] args) { List<UserData> cftLst = new ArrayList<UserData>(); // クラスのオブジェクト初期設定 UserData user1 = new UserData(); UserData user2 = new UserData(); UserData user3 = new UserData(); user1.setUsername("TestUser_01"); user1.setPwd("110"); // リストにオブジェクトの追加 cftLst.add(user1); user2.setUsername("TestUser_02"); user2.setPwd("222"); cftLst.add(user2); user3.setUsername("TestUser_03"); user3.setPwd("333"); cftLst.add(user3); System.out.println("リストの要素(reverse before)"); for (UserData userData : cftLst) { System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd()); } Collections.reverse(cftLst); System.out.println("リストの要素(reverse after)"); for (UserData userData : cftLst) { System.out.println("username: " + userData.getUsername() + " password: " + userData.getPwd()); } } }
3.実行結果
リストの要素(reverse before)
username: TestUser_01 password: 110
username: TestUser_02 password: 222
username: TestUser_03 password: 333
リストの要素(reverse after)
username: TestUser_03 password: 333
username: TestUser_02 password: 222
username: TestUser_01 password: 110