String getChars() method confusion

Question

I am reading from K&B about Strings. For some extra know how, i was reading tutorial from Oracle. I am copying the source code from Oracle.

public class StringDemo {  
    public static void main(String[] args) {  
        String palindrome = "Dot saw I was Tod";  
        int len = palindrome.length();  
        char[] tempCharArray = new char[len];  
        char[] charArray = new char[len];  

        // put original string in an   
        // array of chars  
        for (int i = 0; i < len; i++) {  
            tempCharArray[i] =   
                palindrome.charAt(i);  
        }   

        // reverse array of chars  
        for (int j = 0; j < len; j++) {  
            charArray[j] =  
                tempCharArray[len - 1 - j];  
        }  

        String reversePalindrome =  
            new String(charArray);  
        System.out.println(reversePalindrome);  

        //Testing getChars method //1  
        palindrome.getChars(0, len, tempCharArray, 1);  
        String tempString = new String(tempCharArray);  
        System.out.println(tempString);  
    }  
}

I added point-1 in source code. I was understaning getChars method. When i run it, this program give me ArrayIndexOutOfBoundsException. Here is what i read in String docs.

public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)

Throws: IndexOutOfBoundsException - If any of the following is true: srcBegin is negative. srcBegin is greater than srcEnd srcEnd is greater than the length of this string dstBegin is negative dstBegin+(srcEnd-srcBegin) is larger than dst.length

What is the destBegin? What offset, the documentation is talking about. 1 is a valid offset in destination array. Please help me solve this confusion.

Thanks.

Answer 1

As written in the documentation

the characters are copied into the subarray of dst starting at index dstBegin and ending at index:

 dstbegin + (srcEnd-srcBegin) - 1

so in you case is

1 + (len - 0) -1 = len

note that this is the end Index - so your end index is len but in your array the last index is len -1