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[英]Sorting an ArrayList of Objects by Last name and firstname in Java
[英]Java print last name in arraylist
我有這個
ArrayList<String> players = new ArrayList<String>();
players.add("Albert Pujols");
players.add("Jim Edmonds");
players.add("Josh Hamilton");
players.add("Mike Trout");
players.add("Adrian Gonzalez");
players.add("Price Fielder");
players.add("Steven Strasburg");
players.add("Jose Bautista");
players.add("Bryce Harper");
players.add("Mike Trout");
我將如何制作一種僅打印姓氏的方法:
Pujols
Edmonds
Hamilton
Trout
Gonzalez
Fielder
Strasburg
Bautista
我有這樣的東西,但我卡住了:
public static void printLastName(ArrayList<String> players) {
for (int i = 0; i < players.size(); i++)
System.out.println(players.get(i));
}
我想所有的名字都是用空格隔開的,所以,只需拆分並打印最后一部分
System.out.println(players.get(i).split(" ")[1]);
正如Alexis C所述,您應該使用firstName和lastName創建一個模型類,並將該類實例存儲在List中
您可以只介紹一個Player
類。
public class Player {
final String firstName;
final String lastName;
public Player(final String firstName, final String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
@Override
public String toString() {
return this.lastName;
}
@Override
public boolean equals(final Object o) {
if (this == o) {
return true;
}
if (!(o instanceof Player)) {
return false;
}
final Player player = (Player) o;
if (firstName != null ? !firstName.equals(player.firstName) : player.firstName != null) {
return false;
}
return !(lastName != null ? !lastName.equals(player.lastName) : player.lastName != null);
}
@Override
public int hashCode() {
int result = firstName != null ? firstName.hashCode() : 0;
result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
return result;
}
}
您應該將代碼更改為
public static void printLastName(ArrayList<String> players) {
for (int i = 0; i < players.size(); i++)
System.out.println(players.get(i).split(" ")[1]);
}
只需使用\\\\s
split()
String
函數split()
空間,因為“”在Java中不起作用
這是例子
String lastname = players.get(i).Split("\\s+")[1]; //even split("\\s"); will also work
如果要使用Pattern class
使用以下代碼
private static final Pattern SPACE = Pattern.compile(" ");//outside for loop
String lastname = SPACE.split(players.get(i))[1]; // inside for loop
您可能想讓Arraylist容納一個String數組,例如
ArrayList<String[]> players = new ArrayList<String[]>();
String[] player1 = {"Albert", "Pujols"};
players.add(player1);
System.out.println(players.get(0)[1]);
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