Calc

Calc.java

import java.util.*;

/**
 * 電卓.
 * @author Takashi CHIBA
 */
public class Calc{
	/** 出力モード：分数 */
	private final int OUTPUT_FRACTION = 1;
		
	/** 出力モード：小数 */
	private final int OUTPUT_DECIMAL = 2;
	
	/** charの数値が置いてある範囲 */
	private final int CHAR_NUMBER_START = (int)'0';
	private final int CHAR_NUMBER_END = (int)'9';
	
	/** 対応する演算子 */
	private final char[] supportedOperators = new char[]{'+', '-', '*', '/'};
		
	public static void main(String... args){
		args = new String[1];
		args[0] = "2+3";
		
		switch (args.length) {
			case 1:
				new Calc().runAsFraction(args[0]);
				break;
			
			case 2:
				if (args[0] == "-d") {
					new Calc().runAsDecimal(args[0]);
				}
				break;
				
			case 0:
				System.out.println("数式を入力してください！");
			
			default:
				System.out.println("Usage: java Calc [-d] formura");
		}
	}
	
	public void runAsFraction(String in){
		run(in, OUTPUT_FRACTION);
	}
	
	public void runAsDecimal(String in){
		run(in, OUTPUT_DECIMAL);
	}
	
	/**
	 * 実行する.
	 * @param String in 計算式
	 */
	private void run(String in, int outputType){
		List<Character> rpn = parse(in);
		System.out.println(rpn);
		
//		TODO テスト用に計算式を順番に出すようにしよう！
		calculate(rpn);
	}

	/**
	 * 後置記法(RPN)にする.
	 * @param String in 計算式
	 */
	public List<Character> parse(String in){
		int brackets = 0;
		int skip = 0;
		LinkedList<Character> rpn = new LinkedList<Character>();
		LinkedList<Character> previousOperators = new LinkedList<Character>();
		String operators = new String(supportedOperators);
		
//		TODO 括弧のパースがまずできていない
		for (int i = 0; i < in.length(); i++) {
			char c = in.charAt(i);
			
			/* is SPACE */
			if (c == ' ') {
				continue;
			
			/* is ( */
			} else if (c == '(') {
				brackets++;
			
			/* is ) */
			} else if (c == ')') {
				brackets--;
				rpn.add(previousOperators.pollLast());
			
			/* is Operators(+, -) */
			} else if ("+-".indexOf(c) >= 0) {
				skip = 0;

				while (previousOperators.size() - brackets - skip > 0) {
					rpn.add(previousOperators.pollLast());
//					System.out.println(rpn.getLast());
				}
				
				/* check next operator */
				for (int j = i; j < in.length(); j++) {
					char d = in.charAt(j);
					if (d == '*' || d == '/') {
						skip++;
						break;
					}
				}
				
//				System.out.println("i=" + i + ", c=" + c + ",op=" + previousOperators);
				
				previousOperators.add(c);
				
			/* is Operators(*, /) */
			} else if ("*/".indexOf(c) >= 0) {
				while (previousOperators.size() - brackets - skip > 0) {
					rpn.add(previousOperators.pollLast());
				}
				previousOperators.add(c);
			
			/* is numerical */
			} else if ((int)c >= CHAR_NUMBER_START && (int)c <= CHAR_NUMBER_END) {
				rpn.add(c);
			}
		}
		
		rpn.add(previousOperators.pollLast());
		if (skip == 1) rpn.add(previousOperators.pollLast());
		
		System.out.println(previousOperators);
		
		return rpn;
	}
	
	/**
	 * 計算する.
	 */
	public int calculate(List<Character> rpn){
		for (int i = 2; i < rpn.size(); i++) {
			char c = rpn.get(i);
			
//			TODO 条件減らせる気がする。
			if (c < '0' || c > '9') {
//				TODO 本当に動く？
				int num1 = rpn.get(i - 1) - '0';
				int num2 = rpn.get(i - 2) - '0';
				rpn.remove(i - 2);
				rpn.remove(i - 2);
				
				switch (c) {
				case '+':
					rpn.add(i, num1 + num2);
				case '-':
				
				case '*':
					
				case '/':
					
				}
			}
		}
		
		return result;
	}
	
	
}