java - 当字符串已经被初始化和分配时拒绝声明

Question

我试图接受用户的石头、布、剪刀选择(输入为 r、p 或 s)，但是当我尝试更改并调用它时，它给了我一个错误。

这是我的代码:

package labs10;

import java.util.Scanner;
import static java.lang.System.*;

public class RPSRunner
{
    public static void main(String args[])
    {
        Scanner kb = new Scanner(System.in);
        String full;
        String response;
        String player = "";

        out.print("Select [R,P,S] :: ");
        response = kb.next();
        if (response.equals("R")) {
            full = "Rock";
        } else if (response.equals("P")) {
            full = "Paper";
        } else if (response.equals("S")) {
            full = "Scissors";
        }
        out.println("Player chooses " + full);

        RockPaperScissors game = new RockPaperScissors();   
        game.setPlayers(response);
        game.determineWinner();
        out.println(game);
    }
}

我的错误是

Exception in thread "main" java.lang.Error: Unresolved compilation problem:    The local variable full may not have been initialized        at labs10.RPSRunner.main(RPSRunner.java:25)

Answer 1

String full;

您声明没有初始值的full。如果用户输入 R、P 或 S，您就为其分配一个值。但如果他们输入其他内容怎么办？那么 full 仍然是未初始化的。编译器不喜欢这样。

要么首先为其分配一个值...

String full = null;

...或添加最后的 else 子句来处理所有其他用户输入。

if (response.equals("R")) {
    full = "Rock";
} else if (response.equals("P")) {
    full = "Paper";
} else if (response.equals("S")) {
    full = "Scissors";
} else {
    full = null;
}