尝试在Java中将单个字符推送到Stack时堆内存不足

Question

我正在尝试在Java中为学校的表达式树程序做一个中缀，为了做到这一点，我试图实现一个后缀队列，它是在传递了一个中缀字符串之后构造的，在这个队列中，我使用Java堆栈来持有操作符和左括号，对于shunting-yard算法，表达式树必须使用泛型节点来持有char/int。

当我的程序尝试推送遇到的第一个'(‘时，我遇到了堆内存错误

"Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.base/java.util.Arrays.copyOf(Arrays.java:3511)
    at java.base/java.util.Arrays.copyOf(Arrays.java:3480)
    at java.base/java.util.Vector.grow(Vector.java:262)
    at java.base/java.util.Vector.grow(Vector.java:266)
    at java.base/java.util.Vector.add(Vector.java:782)
    at java.base/java.util.Vector.addElement(Vector.java:617)
    at java.base/java.util.Stack.push(Stack.java:66)
    at project01/project1.PostfixQueue.<init>(PostfixQueue.java:128)
    at project01/project1.ExpressionTree.<init>(ExpressionTree.java:22)
    at project01/project1.Driver.main(Driver.java:11)"

    public PostfixQueue(String infix) {
    Stack<Character> opStack = new Stack<Character>();
    PostfixQueue postQueue = new PostfixQueue();
    
    
    Character digit;
    int numDigits = 0, result = 0;
    
    while(infix.length() > 0) {
        
        digit = (Character) infix.charAt(0);
        
        switch(digit) {
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
        case '0':
            if(numDigits > 0) {
                result = (result * 10) + Character.getNumericValue(digit); //if a result int is previously stored (multi digit int in the string)
                
                if(infix.charAt(1) >= 48 && infix.charAt(1) <= 57) {
                    numDigits++;
                    
                }
                else {
                    //output result
                    postQueue.Enqueue(result);
                    
                    numDigits = 0; //reset numDigits
                }
                
                
            }
            else if(numDigits == 0) {
                if(infix.charAt(1) >= 48 && infix.charAt(1) <= 57) { //If next input is a number w/o whitespace (ex: 45)
                    numDigits++;
                    
                    result = Character.getNumericValue(digit);
                }
                else {
                    numDigits = 0; //reset numDigits
                    
                    //output result
                    postQueue.Enqueue(result);
                }
                
                
            } //End else if
            break;
            
        case '+':
        case '-':
            if(opStack.empty() || opStack.peek() == '(')
            {
                opStack.push(digit);
            }
            else{
                while(opStack.peek() == '+' || opStack.peek() == '-' || opStack.peek() == '*' || opStack.peek() == '/') {
                    //Pop operator and queue it
                    postQueue.Enqueue(opStack.pop());
                    
                }// end while
            }// end else
            opStack.push(digit);
            break;
        case '*':
        case '/':
            while(opStack.peek() == '*' || opStack.peek() == '/') {
                //Pop operator and queue it
                postQueue.Enqueue(opStack.pop());
            }//end while
            opStack.push(digit);
            break;
        case '(':
            opStack.push(digit);
            break;
        case ')':
            while(opStack.peek() != '(') {
                //Pop operator and queue it
                postQueue.Enqueue(opStack.pop());
            }// end while
            
            opStack.pop();
            
            break;
        } // End Switch Statement           
        infix.substring(1);
        
    } // End While Statement            
    this.first = postQueue.GetFirst();
    } // End Constructor

“”“

错误出现在"opStack.push(digit)“处

顶部错误语句第3511行的变量是: copyOf()抛出OutOfMemoryError (id=20)

我如何解决这个问题，这样我才能真正测试整个类的其余部分和其他类的逻辑是否工作？

Answer 1

我发现了问题，我不是偶然地改变了我的循环条件，在接近底部的地方，infix.substring(1);应该是infix = infix.substring(1);，我的程序试图创建一个无限的左括号堆栈。