写中缀到postfix，不知道为什么我的代码抛出一个越界异常

Question

我试图在不使用java的内置堆栈的情况下这样做，所以我创建了一个带有函数的类（如下所示）。我无法弄清楚我的生活中我的逻辑错误导致了错误。

package ass5;
import java.util.*;

public class ass5main{

    public static void main(String[] args) {
        ass5methods pfix = new ass5methods();

        HashMap<Character, Integer> compare = new HashMap<Character, Integer>();
        compare.put('-',1);
        compare.put('+',1);
        compare.put('*',2);
        compare.put('/',2);
        compare.put('(', 3);
        compare.put('{', 3);

        HashMap<Integer, String> errorMsg = new HashMap<Integer, String>(); 
        errorMsg.put(0, "bracket does not match");
        errorMsg.put(1, "parethenses do not match");
        errorMsg.put(2, "order of brackets and parentheses is mixed");
        errorMsg.put(3, "please hardcode an input");

        String[] Statement = new String[5];
        Statement[0] = "(1-1)";
        Statement[1] = "(2+3)";
        Statement[2] = "(3x9) {2+4}";
        Statement[3] = "(2(3*6)}";
        Statement[4] = "{34(26)+10-3}";

        for (Integer i = 0; i <= 4; i++) {
            String postt = "";
            if(Statement[i]!=null) {
                String expression = Statement[i]; 
                boolean correct = true;
                System.out.println("expression" + (i +1));
                for (Integer j = 0; j < expression.length() && correct ; j++) {
                    char c = expression.charAt(j); 
                    if (c >= '0' && c <= '9') {
                        postt +=c;
                    }
                    if (c == '+' || c == '-' || c == '*' || c == '/' ) {
                        if (pfix.stackTop == -1 || compare.get(pfix.read()) <= compare.get(c)) {
                            pfix.push(c);
                        }
                        else if(pfix.stackTop > -1 && compare.get(pfix.read()) >= compare.get(c)){
                            postt += pfix.pop();
                            pfix.push(c);
                        }       }       
                    else if (c == '(' || c == '{' ) {
                        pfix.push(c);
                    }

                    if(c == ')') {
//This while loop is where eclipse says the error is
                        while(!((pfix.topOfStack()) == '(')) {
                            postt += pfix.pop(); 
                        }
                        pfix.pop();
                    }
                    else if(c == '}') {
                        while(!(pfix.read() == '{')) {
                            postt += pfix.pop(); 
                        }
                        pfix.pop();
                    }

                }
            }
            System.out.println(postt);
        }
    }
}
package ass5;
import java.util.*;

public class ass5methods {

    int stackTop;
    public ArrayList <Character> stack2;

    public ass5methods() {
        stackTop = -1;
        stack2 = new ArrayList <Character>();
    }
    public void push(Character c) {
        stackTop++;
        stack2.add(c);
    }   
    public char pop() {

        char c3 = stack2.remove(stackTop);
        stackTop--;
        return c3;
    }
    public char topOfStack() {

        char c = stack2.get(stackTop);
        return c;
    }
    public char read() {
        char c = stack2.get(stackTop);
        return c;
    }

    public boolean isEmpty() {
        if (stackTop<0) {
            return true;
        }
        else {
            return false;
        }
    }


}

Answer 1

public static void main(String[] args) {
    Stack<Character> operators = new Stack();

    HashMap<Character, Integer> compare = new HashMap<Character, Integer>();
    compare.put('-',1);
    compare.put('+',1);
    compare.put('*',2);
    compare.put('/',2);
    compare.put('(', 3);
    compare.put('{', 3);

    HashMap<Integer, String> errorMsg = new HashMap<Integer, String>();
    errorMsg.put(0, "bracket does not match");
    errorMsg.put(1, "parathenses does not match");
    errorMsg.put(2, "order of brackets and paranthese is mixed");
    errorMsg.put(3, "please hardcode an input");

    String[] Statement = new String[5];
    Statement[0] = "(1-1)";
    Statement[1] = "(2+3)";
    Statement[2] = "(3*9) {2+4}";
    Statement[3] = "(2*(3*6)}";
     Statement[4] = "{34*(26)+10-3}";

    for (Integer i = 0; i <= 4; i++) {
        String postt = "";
        if(Statement[i]!=null) {
            String expression = Statement[i];
            boolean correct = true;
            System.out.println("expression" + (i +1));
            for (Integer j = 0; j < expression.length() && correct ; j++) {
                char c = expression.charAt(j);
                if (c >= '0' && c <= '9') {
                    postt +=c;
                }
                if (c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == '{' ) {
                    operators.push(c);
                }
                if(c == ')' || c == '}')  {
                    while(!operators.isEmpty()) {
                        char op = operators.pop();
                        if(op == '(' || op == '{' ) {
                            break;
                        }
                        postt += op;
                    }
                }

            }
        }
        System.out.println(postt);
    }
}

这不是一个完整的解决方案，我改为打印表达式的后缀。我使用了Stack lib类。你可以更新你的选择。刚刚在您的实施更新。这将有助于您更好地发展。可以用这种方式可以试试问题。

1. 了解问题。
2. 写测试用例
3. 把你的逻辑写在纸上。
4. 用您的逻辑验证您的测试用例。
5. 将其转换为代码。