java - 类型不兼容的问题

Question

我是 Java 和学习新手 - 所以请原谅这可能是一个愚蠢的问题!

这是一个简单的剪刀布游戏...

使用 BlueJ 我不断收到此错误；

“不兼容的类型”

运行此代码时；

import comp102.*; 

import java.util.Scanner;


public class RPS{

    String paper = "paper";
    String rock = "rock";
    String scissors = "scissors";    

public void playRound(){

        String paper = "paper";
        String rock = "rock";
        String scissors = "scissors";    

        System.out.print ('\f'); // clears screen
        Scanner currentUserSelection = new Scanner(System.in);

        String enterText = null;
        System.out.println("Make your Selection; Paper, Rock or Scissors: ");
        enterText = currentUserSelection.next();

        System.out.println("enterText = " + enterText);

        if(enterText = paper){
            System.out.println("the IF Stmt is working");
        }

    }

错误指的是这一行“if(enterText = paper){”

非常感谢

Answer 1

您正在尝试在 if 中赋值，这是不允许的

if(enterText = paper)  //here if expects expression which evaluates to boolean  

更改为，

if(enterText == paper)

来自language specs jls-14.9

The if statement allows conditional execution of a statement or a conditional choice of two statements, executing one or the other but not both.

The Expression must have type boolean or Boolean, or a compile-time error occurs.

不要使用 == 运算符，而是使用 String#equals比较字符串。

if(enterText.equals(paper))  //this will compare the String values  

另请参阅

• == and equals difference