String.indexOf()的实现方式

//思想即为在一个大数组中查找一个小数组
public static int indexOf(byte[] source, byte[] target) {   //先把字符串转化为byte[] source，把要查找的字符串转化为byte[]target
    int sourceCount = source.length;  
    int targetCount = target.length;  
    byte first = target[0];  
    int max = (sourceCount - targetCount);  
  
    for (int i = 0; i <= max; i++) {  
        /* Look for first character. */  
        if (source[i] != first) {                          //在source中循环查找出现target的首字符的索引
            while (++i <= max && source[i] != first)  
                ;  
        }  
  
        /* Found first character, now look at the rest of v2 */  
        if (i <= max) {  
            int j = i + 1;  
            int end = j + targetCount - 1;  
            for (int k = 1; j < end && source[j] == target[k]; j++, k++)           // j即为source出现target首字符的位置+1；k即为target数组中首字符+1

                ;  
  
            if (j == end) {  
                /* Found whole string. */  
                return i;  
            }  
        }  
    }  
    return -1;  
}