java stack 问题

我用stack类 进行括号匹配问题。。代码如下
import java.util.*;
public class expTest{
public static void main(String[] args) throws Exception{
Stack stack=new Stack();

Scanner sc=new Scanner(System.in);
System.out.print("请输入一括号表达式：");
String str=sc.next();
String[] list=new String[str.length()];
for(int i=0;i String ss=str.substring(i, i+1);
list[i]=ss;
}

for(int i=0;i
if((list[i].equals(new String("(")))||(list[i]).equals(new String("["))||(list[i].equals(new String("{"))))
stack.push(list[i]);

else if((list[i].equals(new String(")"))) && (stack.peek().equals(new String("("))) && (! stack.isEmpty())){
stack.pop();

}
else if((list[i].equals(new String(")"))) && (! stack.peek().equals(new String("(")))){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String("]"))) && (stack.peek().equals(new String("["))) && (! stack.isEmpty())){
stack.pop();

}
else if((list[i].equals(new String("]"))) && (! stack.peek().equals(new String("[")))){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String("}"))) && (stack.peek().equals(new String("{"))) && (! stack.isEmpty())){
stack.pop();

}
else if((list[i].equals(new String("}"))) && (! stack.peek().equals(new String("{")))){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String(")")))||(list[i].equals(new String("]")))||(list[i].equals(new String("}"))) && (stack.isEmpty())){
System.out.println("右括号多于左括号！");
}
}
if(! stack.isEmpty())
System.out.println("左括号多于右括号！");
else
System.out.println("括号匹配正确！");
}

}
运行，当我这样输入的时候：

请输入一括号表达式：{}}}}
Exception in thread "main" java.util.EmptyStackException

抛出了异常。。。请问这哪里出错了。。求助高手

else if((list[i].equals(new String("}"))) && (! stack.peek().equals(new String("{")))){

stack.peek挂了。
你的判断有问题，第2个}stack已经empty了，你再调用stack.peek()就会挂，判断里的stack.peek().equals(new String。。。这个方法要用之前得先判断stack是否为空。给你改了下循环，后面的输出你看着改把，有问题发消息：

for(int i=0;i
if((list[i].equals(new String("(")))||(list[i]).equals(new String("["))||(list[i].equals(new String("{"))))
stack.push(list[i]);

else if((list[i].equals(new String(")"))) && (stack.peek().equals(new String("("))) && (! stack.isEmpty())){
stack.pop();

}
else if((list[i].equals(new String(")"))) && (! stack.isEmpty())&& (! stack.peek().equals(new String("(")))){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String("]"))) && (! stack.isEmpty())&& (stack.peek().equals(new String("["))) ){
stack.pop();

}
else if((list[i].equals(new String("]"))) && (! stack.isEmpty())&& (! stack.peek().equals(new String("["))) ){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String("}"))) && (! stack.isEmpty())&& (stack.peek().equals(new String("{"))) ){
stack.pop();

}
else if((list[i].equals(new String("}"))) && (! stack.isEmpty())&& (! stack.peek().equals(new String("{"))) ){
System.out.println("左右括号匹配不正确！");
return;
}
else if((list[i].equals(new String(")")))||(list[i].equals(new String("]")))||(list[i].equals(new String("}"))) && (stack.isEmpty())){
System.out.println("右括号多于左括号！");
}
}

我没仔细看你的代码，但是有个问题题我要给你说一下。就是String类的subString(begin,end)方法截取的字符串是String索引位置从begin到(end-1)。你看看你的代码，像你那样截取实际上时没有截取的。

闲着实在无聊...... 写了个简单的双链表实现stack。未引用任何包。 public class main { public static void main(string[] args) { stack s = new stack(); s.put("abc");//压栈 s.put("def");//压栈 s.put("ghi"); system.out.println(s.pop());//出栈 system.out.println(s.isempty());//判断栈是否为空 system.out.println(s.pop()); system.out.println(s.isempty()); system.out.println(s.pop()); system.out.println(s.isempty()); } } class stack { private node root = new node(); private node top = root; public object pop() { if(top != null) { object value = top.getvalue(); top = top.getprevious(); return value; } else { return null; } } public void put(object value) { node n = new node(top, value); top.setnext(n); top = n; } public boolean isempty() { return top.getprevious() == null; } } class node { private node next; private object value; private node previous; public node() { } public node(node previous, object value) { this.previous = previous; this.value = value; } public node getnext() { return next; } public void setnext(node next) { this.next = next; } public object getvalue() { return value; } public void setvalue(object value) { this.value = value; } public node getprevious() { return previous; } public void setprevious(node previous) { this.previous = previous; } }