//http://blog.csdn.net/fightforyourdream/article/details/14642079

public String longestCommonPrefix(String[] strs) {

if (strs == null) {

return null;

}

if (strs.length == 0) {

return "";

}

String s = strs[0];

int len = s.length();

for (int i = 0; i < len; i++) {

char c = s.charAt(i);

for (int j = 1; j < strs.length; j++) {

if (strs[j].length() <= i || c != strs[j].charAt(i)) {

// The char i is invalid. 因为读到i时退出，所以不应包含i本身。

return s.substring(0, i);

}

}

}

// Didn't break, the whole String is valid.

return s;

}