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

Question

我正在与这些一起收到此异常：

java.lang.StringIndexOutOfBoundsException：字符串索引超出范围：Sun处RandomWalk.main（RandomWalk.java:17）处RandomWalk.matchingChoice（RandomWalk.java:50）处java.lang.String.charAt（Unknown Source）处为0。 edu.sun.reflect上的reflect.NativeMethodAccessorImpl.invoke0（本地方法）edu.java.lang.reflect.Method.invoke（未知源）的sun.reflect.DelegatingMethodAccessorImpl.invoke（未知源）的NativeMethodAccessorImpl.invoke（未知源）。 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;
    }
  }
}

错误就在之后

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

我试图将nextLine更改为next，这将允许输入，但在输入后立即会出现相同的错误。 任何帮助将不胜感激，谢谢。

Answer 1

您在CONSOLE.nextLine（）;中犯了一个错误，将其替换为CONSOLE.next（）;。 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

删除扫描仪声明中的最终文件：

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

至

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

然后您将在CONSOLE上实例化一个新的Scanner ，因为您将在CONSOLE Variable上输入其他数据类型。

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

希望能帮助到你。