括号匹配问题

1。判断括号是否成对出现

import java.util.Stack;  

public class KuoHao  
{  
  
    public boolean check(String str)  
    {  
        Stack<Character> stack = new Stack<Character>();  
        boolean flag = true;  
        for (int i = 0; i < str.length() && flag; i++)  
        {  
            try  
            {  
                switch (str.charAt(i))  
                {  
                case '(':  
                case '[':  
                case '{':  
                    stack.push(str.charAt(i));  
                    break;  
                case ')':  
                    if (stack.pop() != '(')  
                        flag = false;  
                    break;  
                case ']':  
                    if (stack.pop() != '[')  
                        flag = false;  
                    break;  
                case '}':  
                    if (stack.pop() != '{')  
                        flag = false;  
                    break;  
                }  
            }  
            catch (Exception e)  
            {  
                flag = false;  
            }  
        }  
        if (flag && !stack.isEmpty())  
            flag = false;  
  
        return flag;  
    }  
  
    public static void main(String[] args)  
    {  
        KuoHao pm = new KuoHao();  
        System.out.println("(: " + pm.check("("));  
        System.out.println("a(bc[d])e{fd}: " + pm.check("a(bc[d])e{fd}"));  
        System.out.println("a(bc]d: " + pm.check("a(bc]d"));  
        System.out.println("a(b(c))d: " + pm.check("a(b(c))d"));  
        System.out.println("a(b)c)d: " + pm.check("a(b)c)d"));  
    }  
}  

2.问题描述：括号成对出现，查找第N个左括号与之匹配的右括号中的内容

　　例如：字符串：A((B)((CD)(E)F)) 查找第1左括号，输出(B)((CD)(E)F)

import java.util.Scanner;

public class KuoHao2 {
	
	public static void search(int N,String s){
		int i = 0,k=-1, w= -1;
		do{
			k = s.indexOf("(",k+1);
			i++;
		}while(i < N && k != -1);
		
		if(k > 0){
			int first = k+1;
			System.out.println("查找字符串\""+s+"\"的第"+N+"个左括号内的内容，匹配起始位于字符串的第:"+(first)+"位");
			w = s.indexOf(")",k+1);
			w = a(w, k, s);
				int end = w;
				System.out.println("匹配结束位于字符串的第:"+(end+1)+"位");
				System.out.println("输出为："+s.substring(first,end ));
			} else {
				System.out.println("不存在')'");
			}
			
		
	}
	

	public static int a(int w, int k, String s){
		if(w > 0){
			int  m =1, n = 1;
			boolean f = false;
			do{
				if(s.indexOf("(",k+1)>0 && s.indexOf("(",k+1) < w){
					k = s.indexOf("(",k+1);
					m += 1;
				}
				while( m > n ){
					while(s.indexOf("(",k+1)>0 && s.indexOf("(",k+1) < w){
						m++;
						k = s.indexOf("(",k+1);
						
					}
					
					for(int j=0; j<=m-n; j++){
						n++;
						w = s.indexOf(")",w+1);
					}
				}
				
				if(s.indexOf("(",k+1)>0 && s.indexOf("(",k+1) < w)
					f = true;
				else f = false;
			}while(f);
		} else {
			System.out.println("不存在'('");
		}
		return w;
	}
		
	public static void main(String[] args) {
		String s = "A((B)((CD)(E)F))";
		Scanner ss =  new Scanner(System.in);
		int N = ss.nextInt();
		search(N,s);
	}

}

　　运行截图：