161. One Edit Distance

public class Solution {
public boolean isOneEditDistance(String s, String t) {
if(s == null || t == null){
return false;
}
if(s.length() == 0 && t.length() == 0){
return false;
}
int m = s.length();
int n = t.length();
if(m<n){ // make sure s的长度永远大于t
String tmp = "";
tmp = s;
s = t;
t = tmp;
}
int diff = Math.abs(m-n);
if (diff > 1) {
return false;
} else if (diff == 1) {
for (int i = 0; i < t.length(); i++) {
if (s.charAt(i) != t.charAt(i)) {
return s.substring(i + 1).equals(t.substring(i));
}
}
return true; //这是为了处理t为空的情况
} else {
for (int i = 0; i < t.length(); i++) {
if (s.charAt(i) != t.charAt(i)) {
return s.substring(i + 1).equals(t.substring(i + 1));
}
}
}
return false;
}
}