leetcode--Valid Parentheses

Given a string containing just the characters

'('

,

')'

,

'{'

,

'}'

,

'['

and

']'

, determine if the input string is valid.

The brackets must close in the correct order,

"()"

and

"()[]{}"

are all valid but

"(]"

and

"([)]"

are not.

public class Solution {
public boolean isValid(String s) {
if(s.length()==0) return true;
Stack<Character> stack = new Stack<Character>();
int i=0;
do{
char cur = s.charAt(i);
if(stack.size()!=0){
switch(cur){
case ']':
if(stack.peek()=='[') stack.pop();
else stack.add(cur);
break;
case '}':
if(stack.peek()=='{') stack.pop();
else stack.add(cur);
break;
case ')':
if(stack.peek()=='(') stack.pop();
else stack.add(cur);
break;
default:
stack.add(cur);
}
}else{
stack.add(cur);
}
i++;
}while(i!=s.length());
if(stack.size()==0) return true;
else return false;
}
}