Tính gần đúng phương trình

BieuThuc.java

package giaipt;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

import bai1_2.KyPhapBaLan;

public class BieuThuc {
	private String bieuthuc = "";
	private int[] heso;
	private int bac;
	public BieuThuc(String bt) {
		this.bieuthuc = bt;
	}
	public BieuThuc(File f) {
		Scanner sc;
		try {
			sc = new Scanner(f);
			if(sc.hasNext()){
				this.bieuthuc = sc.nextLine();
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	// theo phuong phap horner
	public double calc(double x){
		if(heso != null){
			double sum = heso[bac] * x;
	        for (int i = bac - 1 ; i >= 1; i--)
	            sum = (sum + heso[i]) * x;
	        sum += heso[0];
	        return sum;
		}
		else{
			return KyPhapBaLan.calculate(bieuthuc.replace("x", "("+x+")"));
		}
		
	}
	
	public String toString(){
		if(heso != null){
			String s = "";
			for(int i=bac; i>=0; i--){
				s += heso[i] +"x^" + i + " ";
			}
			return s;
		}
		return bieuthuc;
	}
	
	public static void main(String[] args) {
//		BieuThuc dt = new BieuThuc(new File(BieuThuc.class.getResource("dathuc.txt").getPath()));
//		DaThuc dt = new DaThuc("2^x+x-4");
		BieuThuc dt = new BieuThuc("x^3+x-5");
		System.out.println(dt);
		System.out.println(GiaiGanDung.ppchiadoi(dt, 1, 2, 0.0001));
		System.out.println(GiaiGanDung.ppdaycung(dt, 1, 2, 0.0001));
	}
}

GiaiGanDung.java

package giaipt;

public class GiaiGanDung {
	public static double ppchiadoi(BieuThuc dt, double a, double b, double epxilon){
		double c = (b+a)/2.0, E = Math.abs(b-a);
		while(E>epxilon){
//			System.out.println(dt.calc(c));
			if(dt.calc(c)>=0){
				b = c;
			} else{
				a = c;
			}
			E = Math.abs(b-a );
			c = (b+a)/2.0;
		}
		return Math.round(a/epxilon)*epxilon;	
	}

	public static double ppdaycung(BieuThuc bt, double a, double b, double epxilon){
		double x = a - (b-a)*bt.calc(a)/(bt.calc(b)-bt.calc(a));
		double temp = a;
		while(Math.abs(x -temp)> epxilon){
			if(bt.calc(x)*bt.calc(a)<0){
				b = x;
			} else{
				a = x;
			}
			temp = x;
			x = a - (b-a)*bt.calc(a)/(bt.calc(b)-bt.calc(a));
		}
		return Math.round(x/epxilon)*epxilon;
	}

}

KyPhapBaLan.java

package bai1_2;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class KyPhapBaLan {
	public static void main(String[] args) {
		String bieuthuc = "sin((-2.0))";
//		String bieuthuc = "2*(-2.0)+sin((-2))-4";
		ArrayList<String> postfix = InfixToPostfix(bieuthuc);
		System.out.println(postfix);
		float result = calculate(postfix);
		System.out.println(result);
	}
	public static float calculate(String bieuthuc){
		ArrayList<String> postfix = InfixToPostfix(bieuthuc);
		return calculate(postfix);
	}
	
	public static float calculate(ArrayList<String> postfix){
		Stack<Float> stack = new Stack<Float>();
		for(int i=0; i<postfix.size(); i++){
			String s = postfix.get(i);
			if(!isOperator(s) && !isTrigonomicsFunc(s)){
				stack.push(Float.valueOf(s));
			} 
			else if(isTrigonomicsFunc(s)){
				float o = stack.pop();
				float re = 0;
				switch (s) {
				case "sin":
					re = (float) Math.sin(o);
					break;
				case "cos":
					re = (float) Math.cos(o);
					break;
				case "tan":
					re = (float) Math.tan(o);
					break;
				default:
					break;
				}
				stack.push(re);
			}
			else{
				float o1 = stack.pop();
				float o2 = stack.pop();
				float o3 = 0;
				switch (s) {
				case "+":
					o3 = o2+o1;
					break;
				case "-":
					o3 = o2-o1;
					break;
				case "*":
					o3 = o2*o1;
					break;
				case "/":
					o3 = o2/o1;
					break;
				case "%": 
					o3 = o2%o1;
					break;
				case "^":
					o3 = (float)Math.pow(o2, o1);
					break;
				}
				stack.push(o3);
			}
		}
		return stack.pop();
	}
	
	public static int getPriority(String op){
		if("sin".equals(op) || "cos".equals(op) || "tan".equals(op))
			return 4;
		if(op.equals("^"))
			return 3;
		if ("*".equals(op) || "/".equals(op) || "%".equals(op))
	        return 2;
	    if ("+".equals(op) || "-".equals(op))
	        return 1;
	    return 0;
	}
	
	public static boolean isOperator(String str){  // kiem tra xem co phai toan tu
        String operator[] = { "+", "-", "*", "/", ")", "(" , "^"};
        Arrays.sort(operator);
        if (Arrays.binarySearch(operator, str) > -1)
            return true;
        return false;
    }
	
	public static boolean isTrigonomicsFunc(String str){
		return "sin".equals(str) || "cos".equals(str) || "tan".equals(str);
	}
	
	public static ArrayList<String> InfixToPostfix(String infix){
		
		// match 2 | 2.0
		Pattern number = Pattern.compile("^(\\d+\\.\\d+|\\d+)");
		// match (-1) | (-2.3)
		Pattern negative = Pattern.compile("^([(][-](\\d+\\.\\d+|\\d+)[)])");
		Pattern trigfunc = Pattern.compile("^(sin|cos|tan)");
		Stack<String> stack = new Stack();
		ArrayList<String > postfix = new ArrayList<>();
		for(int i=0; i<infix.length(); i++){
//			System.out.println(stack);
//			System.out.println(postfix);
			String s = infix.charAt(i) + "";
			
			if(!isOperator(s) && s.matches("\\d")){
				
				Matcher m = number.matcher(infix.substring(i));
//				System.out.println(infix.substring(i));
				if(m.find()) {
					String num = m.group(0);
					i+= num.length()-1;
					postfix.add(num);
				} 
			} else if(!isOperator(s)){
				Matcher m = trigfunc.matcher(infix.substring(i));
				if(m.find()){
					String trig = m.group(0);
					i+= trig.length()-1;
					stack.add(trig);
				}
		    } else if(s.equals("(")){
		    	Matcher m = negative.matcher(infix.substring(i));
		    	if(m.find()){
		    		// m.group(0) == (-2.0) --need get rid of two ()
		    		String negNum = m.group(0);
		    		i+= negNum.length()-1;
		    		negNum = negNum.substring(1, m.group(0).length()-1);
		    		postfix.add(negNum);
		    	}
		    	else {
//		    		System.out.println(s);
		    		stack.push(s);
		    	}
			} else if(s.equals(")")){
				String x = stack.pop();
				while(!x.equals("(")){
					postfix.add(x);
					x = stack.pop();
				}
			} else {
				
				while(!stack.isEmpty() && getPriority(s) <= getPriority(stack.peek()) && !stack.peek().equals("(")){
					postfix.add(stack.pop());
				}
				stack.push(s);
			}
			
		}
		while(!stack.isEmpty()){
			postfix.add(stack.pop());
		}
		return postfix;
	}
}