leetcode:Valid Anagram

public class Solution {
public boolean isAnagram(String s, String t) {
char[] a=s.toCharArray();
Arrays.sort(a);
String n=String.valueOf(a);
char[] b=t.toCharArray();
Arrays.sort(b);
String m=String.valueOf(b);
if(n.equals(m)) return true;
return false;
}
}

public static boolean isAnagram(String s, String t) {
if(s==null||t==null||s.length()!=t.length()) return false;
int[] dic=new int[256];
char[] ch1=s.toCharArray();
char[] ch2=t.toCharArray();
for(char c:ch1)
{
dic[c]++;
}
for(char c:ch2)
{
if(dic[c]>0)
dic[c]--;
else return false;
}
return true;
}