gptb2.java

Solve a equation in two variables.

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.lcdui.TextField;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;


public class GPTB2 extends MIDlet implements CommandListener{

	private Form fmMain;
	private TextField tfA,tfB,tfC;
	private StringItem siResult;
	private Command cmExit,cmCalc;
	public GPTB2() {
		// TODO Auto-generated constructor stub
		fmMain = new Form("Giai phuong trinh bac 2");
		cmCalc = new Command("Giai",Command.OK,0);
		cmExit = new Command("Exit",Command.EXIT,0);
		tfA = new TextField("He so a","",TextField.NUMERIC,3);
		tfB = new TextField("He so b","",TextField.NUMERIC,3);
		tfC = new TextField("He so c","",TextField.NUMERIC,3);
		siResult = new StringItem("Ket qua :","");
		fmMain.append(tfA);
		fmMain.append(tfB);
		fmMain.append(tfC);
		fmMain.append(siResult);	
		
		fmMain.addCommand(cmCalc);
		fmMain.addCommand(cmExit);
		fmMain.setCommandListener(this);
	}

	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
		// TODO Auto-generated method stub

	}

	protected void pauseApp() {
		// TODO Auto-generated method stub

	}

	protected void startApp() throws MIDletStateChangeException {
		// TODO Auto-generated method stub
		Display.getDisplay(this).setCurrent(fmMain);
	}

	public void commandAction(Command cm, Displayable d) {
		// TODO Auto-generated method stub
		if(cm==cmExit){
			notifyDestroyed();
		} else if(cm==cmCalc){
			float dt,a,b,c,x1,x2;
			a=Float.parseFloat(tfA.getString());
			b=Float.parseFloat(tfB.getString());
			c=Float.parseFloat(tfC.getString());
			dt = b*b -4*a*c;
			if(dt<0){
				siResult.setText("Phuong trinh vo nghiem");
			} else if(dt==0){
				x1=-b/(2*a);
				siResult.setText("Phuong trinh co 1 nghiem la " + x1);
			} else {
				x1=(-b+(float)Math.sqrt(dt))/(2*a);
				x2=(-b-(float)Math.sqrt(dt))/(2*a);
				siResult.setText("Phuong trinh co 2 nghiem la " + x1 + " va " + x2);
			}
			tfA.setString("");
			tfB.setString("");
			tfC.setString("");
		}
	}

}