Question

import java.io.*;
public class Program
{
    public static void main(String args[])throws IOException
    {
        InputStreamReader isr = new InputStreamReader (System.in);
        BufferedReader br = new BufferedReader (isr);
        int i, len;
        char ch;
        String rev = "";
        System.out.println("Enter a String:");
        String str = br.readLine();
        len = str.length();
        for(i=len; i>=0; i--)
        {
            ch = str.charAt(i);
            rev = rev + ch;
        }
        System.out.println("Reversed String is: " +rev);
    }
}

该程序正常工作，直到输入后按Enter键。例如输入字符串：

的java

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 5
at java.lang.String.charAt(String.java:658)
at Program.main(Program.java:16)
Java Result: 1

我尝试在NetBeans中编译它。请解释一下。

Answer 1

使用for(i=len-1; i>=0; i--)而非for(i=len; i>=0; i--)，否则str.charAt(i)将在for循环的第一次迭代中超出字符串的最后一个字符。

String str = "ABCDE";   // for example
int len = str.length(); // 5

"ABCDE"  (your string)
 01234   (index)

str.charAt(0) // 'A'
str.charAt(len-1)  // 'E'
str.charAt(len)    // StringIndexOutOfBoundsException occurs

DEMO

Answer 2

请考虑使用StringBuffer的reverse（）方法：

import java.io.*;
public class Program
{
    public static void main(String args[]) throws IOException
    {
        InputStreamReader isr = new InputStreamReader (System.in);
        BufferedReader br = new BufferedReader (isr);
        System.out.println("Enter a String:");
        StringBuffer sbInput = new StringBuffer(br.realLine());
        System.out.println("Reversed String is : " + sbInput.reverse());
    }
}

字符串索引超出范围

2 个答案: