longest common prefix

public class  {
    public String longestCommonPrefix(String[] strs) {
        if(strs==null||strs.length==0) return "";
        String pre = strs[0];
        for(int i=1;i<strs.length;i++) {
            while(strs[i].indexOf(pre)!=0) {
                pre = pre.substring(0,pre.length()-1);
            }
        }
        return pre;
    }
}