Token.java

package com.johnChnia.coding2017.basic.stack.expr;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class Token {
    public static final List<String> OPERATORS = Arrays.asList("+", "-", "*", "/");
    public static final List<String> OPENINGPARENTHESES = Arrays.asList("(", "[", "{");
    public static final List<String> CLOSINGPARENTHESES = Arrays.asList(")", "]", "}");
    private static final Map<String, Integer> priorities = new HashMap<>();

    static {
        priorities.put("+", 1);
        priorities.put("-", 1);
        priorities.put("*", 2);
        priorities.put("/", 2);
        priorities.put("(", 0);
        priorities.put("[", 0);
        priorities.put("{", 0);
    }

    static final int OPERATOR = 1;
    static final int NUMBER = 2;
    static final int PARENTHESES = 3;
    String value;
    int type;

    public Token(int type, String value) {
        this.type = type;
        this.value = value;
    }

    public boolean isNumber() {
        return type == NUMBER;
    }

    public boolean isOperator() {
        return type == OPERATOR;
    }

    public int getIntValue() {
        return Integer.valueOf(value).intValue();
    }

    public String toString() {
        return value;
    }

    public boolean hasHigherPriority(Token t) {
        if (!this.isOperator() && !t.isOperator()) {
            throw new RuntimeException("numbers can't compare priority");
        }
        return priorities.get(this.value) - priorities.get(t.value) > 0;
    }

    public boolean isOpeningParentheses() {
        return OPENINGPARENTHESES.contains(this.value);
    }

    public boolean isClosingParentheses() {
        return CLOSINGPARENTHESES.contains(this.value);
    }
}