Quick Links;
1. How to start JavaFx Project
How to install Java https://s08kzivyri.vmaker.com/record/CdIy2tyin1BrtFeg
java codes;
======1. How to find a prime number;======================
get number and find modulus with each i number from 1 to given number
num%i ; where i=1;i<num;i++ ;
if num%i==0; then the number is composite; else it a prime.
import java.util.*;
class Example{
public static String isPrime(int num){
boolean isPrime=true;
for(int j=2; j<num; j++){
if(num%j==0){
isPrime=false;
break;
}
}
return isPrime ? " prime ": " Not Prime";
}
public static void main(String args[]){
Scanner input = new Scanner(System.in);
System.out.print("Input a number : ");
int num = input.nextInt();
System.out.print(num + isPrime(num));
}
}
=====How to find prime number using two loops L1 and L2 =========
class Example{
public static void main(String args[]){
L1: for(int i=3; i<=100; i++){ // create loop L1: and increase i values by 1
L2:for(int j=2; j<i; j++){ // create loop L2: and increase j from 2 to i-1;
if(i%j==0){ // if i can devide by j
continue L1; // continue loop L1
}
}
System.out.println(i);
}
}
}
=======================================================
class Example{
public static void main(String args[]){
int num=43;
int count=0;
for(int j=2; j<num; j++){ // devide number from 2 to 42,
if(num%j!=0){ //check wether reminder is not equal to zero
count++; // count number of this kind of cycles
}
}
if(count==num-2){ // if all numbers devide with reminders
System.out.println(num+" is a primne number");
}
}
}
========= How to find a factorial using java methods================
import java.util.*;
class Example{
public static int findFactorial(int num){
if( num>0){
return num*findFactorial(num-1);}
else{
return 1;}
}
public static void main ( String args[]){
Scanner input = new Scanner (System.in);
System.out.print("Insert a number to find its factorial : ");
int number = input.nextInt();
System.out.print("Factrial of "+ number + "! =" + findFactorial(number));
}
}
============= Reverse a given string =========================
import java.util.*;
public class Example{
public static String reverse (String str){
char ch[]=str.toCharArray();
String rev= "";
for ( int i=ch.length-1;i>=0;i--){
rev+=ch[i];
}
return rev;
}
public static void main(String args[]){
String str = "Asanka";
System.out.println(reverse(str));
}
}
How to alternate Array
import java.util.*;
class Example{
public static int[] ar={34,12,61,29,59,94,24,58};
public static void main(String args[]){
System.out.println(Arrays.toString(ar)); //[34,12,61,29,59,94,24,58]
System.out.println("Length : "+ar.length); //8
add(99);
System.out.println(Arrays.toString(ar));//[34,12,61,29,59,94,24,58,99]
System.out.println("Length : "+ar.length); //9
add(55,4); //add(int data, int index)
System.out.println(Arrays.toString(ar));//[34,12,61,29,55,59,94,24,58,99]
System.out.println("Length : "+ar.length); //10
remove(4); //remove(index)
System.out.println(Arrays.toString(ar));//[34,12,61,29,59,94,24,58,99]
System.out.println("Length : "+ar.length); //9
add(new int[]{10,20,30,40},4); //add(int[] arrayElement, int index)
System.out.println(Arrays.toString(ar));//[34,12,61,29,10,20,30,40,59,94,24,58,99]
System.out.println("Length : "+ar.length); //13
remove(4,7); //remove(int startIndex, int endIndex)
System.out.println(Arrays.toString(ar));//[34,12,61,29,59,94,24,58,99]
System.out.println("Length : "+ar.length); //9
}
public static void add(int data){ //add to the last
int[] temp=new int[ar.length+1];
for (int i = 0; i < ar.length; i++){
temp[i]=ar[i];
}
ar=temp;
ar[ar.length-1]=99;
}
//overload method add
public static void add(int data, int index){ //add to the index
if(index>=0 && index<ar.length){
int[] temp=new int[ar.length+1];
for (int i = 0; i < ar.length; i++){
temp[i]=ar[i];
}
for (int i = temp.length-1; i >index; i--){
temp[i]=temp[i-1];
}
temp[index]=data;
ar=temp;
}else{
System.out.println("Index error");
}
}
// remove int
public static void remove(int index){
int [] temp = new int [ar.length-1];
for (int i = 0; i < index; i++) {
temp[i]=ar[i];
}
for (int i = index ;i<temp.length; i++) {
temp[i]=ar[i+1];
}
ar=temp;
}
// add array
public static void add(int [] addAr,int index){
int[] temp = new int [(ar.length+addAr.length)];
for (int i = 0; i < index; i++) {
temp[i]=ar[i];
}
for (int i = index; i < (addAr.length+index-1); i++) {
temp[i]=addAr[i-index];
}
for (int i = (addAr.length+index-1); i <(ar.length+addAr.length); i++) {
temp[i]=ar[i-(addAr.length+index-1)];
}
ar=temp;
}
public static void remove(int index1, int index2){
int [] temp = new int [ar.length-(index2-index1+1)];
for (int i = 0; i < index1; i++){
temp[i]=ar[i];
}
for (int i = index2+1; i < ar.length; i++) {
temp[i-index1] = ar[i];
}
ar=temp;
}
}
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;
import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
class Calculator extends JFrame implements ActionListener //
{
private JPanel buttonPanel;
private JPanel inputOutputPanel;
private JTextField info;
private boolean editable = true;
public Calculator()
{
Container contentPane = getContentPane();
contentPane.setLayout(new FlowLayout());
buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(4,4,5,5));
//for padding
buttonPanel.setBorder(new EmptyBorder(10,10,10,10));
inputOutputPanel = new JPanel();
inputOutputPanel.setLayout(new FlowLayout());
setTitle("Calculator using Java");
setSize(400,320);
setResizable(false);
info = new JTextField();
info.setFont(new Font("SansSerif", Font.PLAIN, 16));
info.setBackground(Color.white);
info.setBorder(BorderFactory.createLineBorder(Color.black));
info.setPreferredSize(new Dimension(180, 25));
info.addActionListener(this);
inputOutputPanel.add(info);
contentPane.add(inputOutputPanel);
//buttons in calculator
String buttons[] = {"7", "8", "9", "/", "4", "5", "6", "*", "1", "2","3","-","0",".","=", "+",};
//adding buttons for buttons array
for (String i : buttons)
{
JButton button = new JButton(i);
button.addActionListener(this);
buttonPanel.add(button);
}
contentPane.add(buttonPanel);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
public void actionPerformed(ActionEvent event)
{
//source is from button
if (event.getSource() instanceof JButton)
{
JButton clickedButton = (JButton) event.getSource();
//if = is clicked then result will be displayed
if(clickedButton.getText().equals("="))
{
addOutput();
}
//else we will take input
else
{
addInput(clickedButton.getText());
}
}
//source is from JTextField
else
{
addOutput();
}
}
public void addInput(String line)
{
//appending pressed keys to TextField
//editable will be false if result is displayed
if(editable)
{
info.setText(info.getText()+line);
}
//result is on the screen
//editable is false
//no appending
//we will add the text
else
{
info.setText(line);
editable = true;
}
}
public void addOutput()
{
double output = 0;
//converting string into expression
try
{
ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
info.setText(engine.eval(info.getText()).toString());
}
catch(ScriptException e)
{
info.setText("Syntax error");
}
editable = false;
}
//main method
public static void main (String [] args)
{
Calculator calculator = new Calculator();
calculator.setVisible(true);
}
}
public void park(){
System.out.println("Vehicle Parking..");
}
}
class Car extends Vehicle{
public void park(){ //Same name, same parameter list==>Method Overriding
System.out.println("Car Parking..");
}
}
class Demo{
public static void main(String args[]){
Vehicle v1=new Car();
v1.park(); //(Car Parking...) Compile from Vehicle Class but Run from Car Class
}
}
public void park(){
System.out.println("Vehicle Parking..");
}
}
class Car extends Vehicle{ // Car class inherit from Vehicle super class
//Same name, same parameter list==>Method Overriding
//if same name different parameter ==> Methods Overloading
public void park(){
System.out.println("Car Parking..");
}
}
class Van extends Vehicle {
public void park (){
System.out.println("Van Parking..");
}
}
class Bus extends Vehicle{
public void park(){
System.out.println("Bus Parking .. ");
}
}
class Demo{
public static void main(String args[]){
//create Vehicle object array
Vehicle [] vehicleArray = {new Car(),new Van(), new Car(), new Bus()};
for(Vehicle v1: vehicleArray){ // For Each loop to create V1 object
v1.park(); // single interface many output form ==> polymorphism
}
}
}
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