Tokenize the string

I try to tokenize an expression like ( 3 < 5 ) or ( 5 > 10 )

I wrote the code, but it can not see the comparison operators and so can not compare integers. Can you please advise to how to fix this?

The result should be true or false.

public class StackMain {
    public static void main(String[] args) {
        String FileData = "test";
        FileReader readFile = null;
        try {
            readFile = new FileReader(FileData);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        BufferedReader reader = new BufferedReader(readFile);
        String inputFile;
        try {
            inputFile = reader.readLine();
            while (inputFile != null) {
                processInputData(inputFile);
                inputFile = reader.readLine();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void processInputData(String str) {
        ArrayStack<Integer> intNum = new ArrayStack<>();
        ArrayStack<String> operVal = new ArrayStack<>();

        String[] subStr = str.split(" ");
        for (int i = 0; i < subStr.length; i++) {
            if (subStr[i].charAt(0) >= '0' && subStr[i].charAt(0) <= '9') {
                intNum.push(Integer.parseInt(subStr[i]));
            } else if (subStr[i] == "<" || subStr[i] == ">" || subStr[i] == "==" || subStr[i] == "||"
                    || subStr[i] == "&&") {
                operVal.push(subStr[i]);
            } else if (subStr[i] == ")") {
                int A = intNum.pop();
                int B = intNum.pop();
                String oper = operVal.pop();
                if (oper == "<") {
                    intNum.push(A < B ? 1 : 0);
                } else if (oper == ">") {
                    intNum.push(A > B ? 1 : 0);
                } else if (oper == "==") {
                    intNum.push(A == B ? 1 : 0);
                } else if (oper == "||") {
                    intNum.push(A | B);
                } else if (oper == "&&") {
                    intNum.push(A & B);
                }
            }
        }
        System.out.println("The value of " + str + "is " + (intNum.pop() == 1));
    }
}

>Solution :

You need to pop B, before you pop A.

int B = intNum.pop();
int A = intNum.pop();

Since it is a stack, B was added last, so it needs to be popped off first.

Also, don’t forget to call close() on any readers you may have initialized.

import java.io.*;
import java.util.*;

public class StackMain {
    public static void main(String[] args) {
        String filename = "test";
        FileReader fileReader = null;
        try {
            fileReader = new FileReader(filename);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        String inputFile;
        try {
            inputFile = bufferedReader.readLine();
            while (inputFile != null) {
                processInputData(inputFile);
                inputFile = bufferedReader.readLine();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            fileReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void processInputData(String str) {
        Deque<Integer> intNum = new ArrayDeque<>();
        Deque<String> operVal = new ArrayDeque<>();
        String[] tokens = str.split(" ");
        for (int i = 0; i < tokens.length; i++) {
            switch (tokens[i]) {
                case "0":
                case "1":
                case "2":
                case "3":
                case "4":
                case "5":
                case "6":
                case "7":
                case "8":
                case "9":
                    intNum.push(Integer.parseInt(tokens[i]));
                    break;
                case "<":
                case ">":
                case "==":
                case "||":
                case "&&":
                    operVal.push(tokens[i]);
                    break;
                case ")":
                    int B = intNum.pop();
                    int A = intNum.pop();
                    String oper = operVal.pop();
                    switch (oper) {
                        case "<":
                            intNum.push(A < B ? 1 : 0);
                            break;
                        case ">":
                            intNum.push(A > B ? 1 : 0);
                            break;
                        case "==":
                            intNum.push(A == B ? 1 : 0);
                            break;
                        case "||":
                            intNum.push((A | B) == 1 ? 1 : 0);
                            break;
                        case "&&":
                            intNum.push((A & B) == 1 ? 1 : 0);
                            break;
                    }
                    break;
            }
        }
        System.out.printf("The value of %s is %b%n", str, (intNum.pop() == 1));
    }
}

Input (filename: test)

( 3 < 5 )

Output

The value of ( 3 < 5 ) is true