Java 错误 java.lang.StringIndexOutOfBoundsException：字符串索引超出范围：0

Question

我收到了这个异常以及这些：

java.lang.StringIndexOutOfBoundsException：字符串索引超出范围： 0 在 java.lang.String.charAt(Unknown Source) 在 RandomWalk.matchingChoice(RandomWalk.java:50) 在 RandomWalk.main(RandomWalk.java:17) 在 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 在 sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke（未知来源）在 java.lang.reflect.Method.invoke（未知来源）在 edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:267)

运行此代码时：

import java.util.*;
import java.awt.*;
public class RandomWalk{
  public static final Scanner CONSOLE = new Scanner(System.in);
  public static void main(String[] args){
    System.out.println("Enter Circle Radius (50-400):");
    int radius = CONSOLE.nextInt();
    while (radius < 50 || radius > 400){
      System.out.println("Radius Invalid; Try Again");
      System.out.println("Enter Circle Radius (50-400):");
      radius = CONSOLE.nextInt();
    }
    int diameter = radius*2;
    int panelD = diameter/4;
    System.out.println("Enter Color of Circle (Blue or Green)");
    String colorChoice = CONSOLE.nextLine();
    boolean test = matchingChoice(colorChoice, "blue");
    boolean test2 = matchingChoice(colorChoice, "green");
    while(test2 == false && test == false){
      System.out.println("Invalid Entry Try Again");
      System.out.println("Enter Color of Circle (Blue or Green)");
      colorChoice = CONSOLE.nextLine();
      test = matchingChoice(colorChoice, "blue");
      test2 = matchingChoice(colorChoice, "green");
    }
    if(test == true){
      Color circleColor = Color.BLUE;
    } else {
      Color circleColor = Color.GREEN;
    }
    System.out.println("Enter Color of Walk Path (Orange or Red)");
    colorChoice = CONSOLE.nextLine();
    test = matchingChoice(colorChoice, "orange");
    test2 = matchingChoice(colorChoice, "red");
    while(test2 == false && test == false){
      System.out.println("Invalid Entry Try Again");
      System.out.println("Enter Color of Circle (Orange or Red)");
      colorChoice = CONSOLE.nextLine();
      test = matchingChoice(colorChoice, "orange");
      test2 = matchingChoice(colorChoice, "red");
    }
    if(test == true){
      Color pathColor = Color.ORANGE;
    } else {
      Color pathColor = Color.RED;
    }
  }
  public static boolean matchingChoice(String input, String choice){
    input = input.toLowerCase();
    char fLI = input.charAt(0);
    char fLC = choice.charAt(0);
    if(fLI == fLC){
     return true;
    } else if (input.equals(choice)){
      return true;
    } else {
      return false;
    }
  }
}

错误发生在

之后

System.out.println("Enter Color of Circle (Blue or Green)");

我尝试将 nextLine 更改为 next，这将允许输入，但在输入后会出现相同的错误。任何帮助将不胜感激，谢谢。

Answer 1

你在 CONSOLE.nextLine(); 中犯了一个错误，像 CONSOLE.next(); 一样替换它 并且您的代码将正确运行。

String colorChoice = CONSOLE.next();

将所有CONSOLE.nextLine() 替换为CONSOLE.next()

Answer 2

删除您的扫描仪声明中的最后一个：

public static final Scanner CONSOLE = new Scanner(System.in);

到

public static Scanner CONSOLE = new Scanner(System.in);

然后您将在您的CONSOLE 上实例化一个新的Scanner，因为您将在您的CONSOLE Variable 上输入不同的数据类型。

System.out.println("Enter Color of Circle (Blue or Green)");
CONSOLE = new Scanner(); // Instantiate new Scanner on your CONSOLE variable
colorChoice = CONSOLE.nextLine();

希望对你有帮助。