Question

我在这行代码中遇到错误：while（s.charAt（i - 1）！=＆＃39; \ 0＆＃39;）。我尝试使用开关比较输入字符串，这里是整个代码：

public static int Main()
{
String s = new String(new char[20]);
byte c;
int state = 0;
int i = 0;

System.out.print("\n Enter a string:");
s = new Scanner(System.in).nextLine();
while (s.charAt(i - 1) != '\0')
{
         char result = s.charAt(i);
  System.out.println(result);

 switch (state)
 {
 case 0:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 1;
 }
 else if (c == (byte)'b')
 {
 state = 2;
 }
 else
 {
 state = 6;
 }
 break;
 case 1:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 3;
 }

 else if (c == (byte)'b')
 {
 state = 4;
 }
else
{
 state = 6;
}
 break;
 case 2:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 6;
 }
 else if (c == (byte)'b')
 {
 state = 2;
 }
else
{
 state = 6;
}
 break;
 case 3:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 3;
 }
 else if (c == (byte)'b')
 {
 state = 2;
 }
else
{
 state = 6;
}
 break;
 case 4:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 6;
 }

 else if (c == (byte)'b')
 {
 state = 5;
 }
else
{
 state = 6;
}
 break;
 case 5:
     c = (byte) s.charAt(i++);
 if (c == (byte)'a')
 {
 state = 6;
 }
 else if (c == (byte)'b')
 {
 state = 2;
 }
else
{
 state = 6;
}
 break;
 case 6:
     System.out.printf("\n %s is not recognised.",s);
 System.exit(0);
 }
}

if (state == 1)
{
 System.out.printf("\n %s is accepted under rule 'a'",s);
}
 else if ((state == 2) || (state == 4))
 {
System.out.printf("\n %s is accepted under rule 'a*b+'",s);
 }
 else if (state == 5)
 {
 System.out.printf("\n %s is accepted under rule 'abb'",s);
 }
        return 0;

}

它表示字符串索引超出范围。我也尝试显示字符（i）它显示正确的字符串，但我不知道为什么我有这个错误

Answer 1

您正在使用int i = 0;，然后检查while (s.charAt(i-1) != '\0')。当您将i设置为0时，i-1将为-1和StringIndexOutOfBoundsException 会发生。所以使用int i = 1;或while (s.charAt(i) != '\0')

字符串索引超出范围而条件

1 个答案: