BigNumTester

package bignumTester;

import java.math.BigInteger;
import java.util.ArrayList;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.RowConstraints;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class BigNumTester extends Application {

	private BigInteger rsaVal;
	private BigInteger dVal;
	private BigInteger ddVal;
	private BigInteger eVal;
	private BigInteger xVal;
	private BigInteger bigNVal;

	private static final int WIDTH = 1024;
	private static final int HEIGHT = 768;
	private static final int NUMCOLS = 5;
	private static final int NUMROWS = 5;
	private static final int COL1_PERCENT_WIDTH = 10;
	private static final int OTHERCOLS_PERCENT_WIDTH = (100 - COL1_PERCENT_WIDTH);
	private static final int PADDING= 10;


	@Override
	public void start(Stage primaryStage) {
		GridPane root = new GridPane();
		setupGrid(root);
		addComponents(root);

		Scene scene = new Scene(root, WIDTH, HEIGHT);
		scene.getStylesheets().add
			(BigNumTester.class.getResource("bigNumTester.css").toExternalForm());

		primaryStage.setTitle("BigNumTester");
		primaryStage.setScene(scene);
		primaryStage.show();
	}

	public static void main(String[] args) {
		launch(args);
	}

	private void setupGrid(GridPane root){
		ArrayList<ColumnConstraints> ccArray = new ArrayList<>();
		ColumnConstraints c1 = new ColumnConstraints();
		c1.setPercentWidth(COL1_PERCENT_WIDTH);
		ccArray.add(c1);

		for(int i = 1; i < NUMCOLS; i++){
			ColumnConstraints temp = new ColumnConstraints();
			temp.setPercentWidth(OTHERCOLS_PERCENT_WIDTH/(NUMCOLS - 1));
			ccArray.add(temp);
		}

		ArrayList<RowConstraints> rcArray = new ArrayList<>();
		for(int j = 0; j < NUMROWS; j++){
			RowConstraints temp = new RowConstraints();
			temp.setPercentHeight(100/NUMROWS);
			rcArray.add(temp);
		}
		root.getColumnConstraints().addAll(ccArray);
		root.getRowConstraints().addAll(rcArray);
	}
	private void addComponents(GridPane root){
		Text rsaLbl = new Text("RSA2048:");
		TextArea rsaIn = new TextArea();
		rsaIn.setPrefColumnCount(WIDTH * OTHERCOLS_PERCENT_WIDTH / 100);
		rsaIn.setPrefRowCount(100/NUMROWS * 1 * HEIGHT);
		rsaIn.setWrapText(true);

		Text dLbl = new Text("d: ");
		TextArea dResult = new TextArea("");
		dResult.setPrefColumnCount(WIDTH * OTHERCOLS_PERCENT_WIDTH / 100);
		dResult.setPrefRowCount(100/NUMROWS * 1 * HEIGHT);
		dResult.setWrapText(true);

		Text eLbl = new Text("e: ");
		TextArea eResult = new TextArea("");
		eResult.setPrefColumnCount(WIDTH * OTHERCOLS_PERCENT_WIDTH / 100);
		eResult.setPrefRowCount(100/NUMROWS * 1 * HEIGHT);
		eResult.setWrapText(true);

		Text bigNLbl = new Text("N: ");
		TextArea bigNResult = new TextArea("");
		bigNResult.setPrefColumnCount(WIDTH * OTHERCOLS_PERCENT_WIDTH / 100);
		bigNResult.setPrefRowCount(100/NUMROWS * 1 * HEIGHT);
		bigNResult.setWrapText(true);

		Button runBtn = new Button("Go!");
		runBtn.setAlignment(Pos.BOTTOM_RIGHT);
		runBtn.setOnAction(new EventHandler<ActionEvent>(){
			@Override
			public void handle(ActionEvent e){
				rsaVal = new BigInteger(rsaIn.getText());
				dVal = Sqrt(rsaVal);
				dResult.setText(dVal.toString());
				ddVal = dVal.multiply(dVal);
				eVal = rsaVal.subtract(ddVal);
				eResult.setText(eVal.toString());
				xVal = dVal.subtract(BigInteger.ONE);
				bigNVal = rsaVal.subtract(BigInteger.ONE).divide(new BigInteger("2")).subtract(xVal);
				bigNResult.setText(bigNVal.toString());
			}
		});

		root.add(rsaLbl,0,0);
		root.add(rsaIn,1,0,4,1);
		root.add(dLbl,0,1);
		root.add(dResult,1,1,4,1);
		root.add(eLbl,0,2);
		root.add(eResult,1,2,4,1);
		root.add(bigNLbl,0,3);
		root.add(bigNResult,1,3,4,1);
		root.add(runBtn,4,4,2,1);
	}
	//https://stackoverflow.com/questions/4407839/how-can-i-find-the-square-root-of-a-java-biginteger
	public static BigInteger Sqrt(BigInteger number){
		BigInteger high = BigInteger.ZERO.setBit(number.bitLength()/2);
		BigInteger low = high;
		if (number == BigInteger.ZERO){
			 return BigInteger.ZERO;
		}
		for(;;){
			 BigInteger n = high.add(number.divide(low)).shiftRight(1);
			 //This conditional has been modified; it may have to be reevaluated if there are problems.
			 //As it was, it was seeking the closest of -either- the higher or lower perfect square:
			 //if(n.equals(high) || n.equals(low)){
			 if(n.equals(low) || n.equals(BigInteger.ZERO)){
				 return n;
			 }
			 low = high;
			 high = n;
		}
	}
}


css file (name it "bigNumTester.css", place in the same file as the above file (which should be named "BigNumTester.java"):

.root {
	-fx-background-color: gainsboro;
	-fx-font-family: "Century Gothic";
	-fx-font-size: 14pt;
}
.text {
	-fx-font-size: 16pt;
	-fx-font-family: "Century Gothic";
}
.text-area {
	-fx-font-size: 10pt;
	-fx-font-family: "Century Gothic";
}