異常在線程 「主」 java.lang.StringIndexOutOfBoundsException：字符串索引超出範圍：-18

Question

這是我的代碼

import java.util.Scanner; 
import java.io.*; 

class Main { 
public static void main (String[] args)throws IOException { 
    Scanner scan = new Scanner(System.in); 
    System.out.println ("Enter message board post:"); 
    String username = scan.nextLine(); 
    String check = username.substring (username.indexOf(" ")+3 , username.length()).toLowerCase()+" "; 
    int a = check.indexOf(" ^^ "); 
    int b = check.indexOf (" qey "); 
    int c = check.indexOf (" $ "); 
    String first = username.substring (0 , username.indexOf(" ")); 
    int x = 0; 
    int y =0; 
    int z = 0; 
    while (a != -1) { 
    x++; 
    check = check.substring(a+1, check.length()); 
    a = check.indexOf(" ^^ "); } 
    while (b != -1) { 
    y++; 
    check = check.substring(b+1, check.length()); 
    b = check.indexOf(" qey "); } 
    while (c != -1) { 
    z++; 
    check = check.substring(c+1, check.length()); 
    c = check.indexOf (" $ "); } 
    if (x > 0 || y > 0 || z > 0){ 
    System.out.println (""); 
    System.out.println ("BAD"); 
     System.out.println (first); 
     System.out.println ("^^: " +x); 
     System.out.println ("qey: " +y); 
     System.out.println ("$: " +z); 

    }else { 
     System.out.println (""); 
     System.out.println ("CLEAN"); 
    } 
    } 
} 

在端部的結果是：

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -18 
at java.lang.String.substring(String.java:1967) 
at Main.main(Main.java:23) 

哪些部分我必須改變擺脫線程？ 我輸入B0rg - 抵抗是徒勞的QeY哈哈哈哈$$$ ^^

，它應該顯示爲

BAD 
B0rg 
^^: 1 

qey：1 $：0

但它顯示了作爲例外。 ..請幫我...

Answer 1

我假設你只輸入一個單詞，因爲如果你輸入兩個，它工作正常。它失敗了，因爲它正在尋找一個子字符串，除非有兩個單詞被你的分隔符分隔，而這恰好是一個空格。