A8:字符串查找

 1 class Solution {
 2     /**
 3      * Returns a index to the first occurrence of target in source,
 4      * or -1  if target is not part of source.
 5      * @param source string to be scanned.
 6      * @param target string containing the sequence of characters to match.
 7      */
 8     public int strStr(String source, String target) {
 9         // write your code here
10         if(source == null || target == null){
11             return -1;
12         }
13         int a = source.indexOf(target);
14         return a;
15     }
16 }