20. valid parentheses

public class Solution {
    private char[] stack =  new char[100];
    private int top = -1;
    
    private void push(char x){
        stack[++top] = x;
    }
   
    private void pop(){
       top--;
    }
    public boolean isValid(String s) {
        char[] str = s.toCharArray();
        int length = str.length;
        try{
              for(int i = 0; i < length ;i++) {
               switch(str[i]){
                   case '(':
                       push(str[i]);
                       break;
                   case '[':
                       push(str[i]);
                       break;
                   case '{':
                       push(str[i]);
                       break;
                   case ')':
                       if(stack[top] == '(') {
                           pop();
                       }
                       else {
                         return false;  
                       }
                       break;
                   case ']':
                        if(stack[top] == '[') {
                           pop();
                       }
                       else {
                         return false;  
                       }
                       break;
                   case '}':
                        if(stack[top] == '{') {
                           pop();
                       }
                       else {
                         return false;  
                       }
                       break;
                   default:
                        return false;
               }
            }  
        }
        catch(Exception e) {
            return false;
        }
        if(top == -1) {
            return true;
        }
        else {
            return false;
        }
    }
}