Java Tongue

Java Program to Solve Tower of Hanoi Puzzle Problem

This is a java program to solve towers of hanoi puzzle problem. This simple java program gives solution for tower of hanoi problem with any number of disks. Tower of Hanoi is a mathematical game or puzzle. It is also called tower of brahma or Lucas' tower. There are three towers (or rods) and a number of disks of different diameters. Initially, The disks have hole at center so that it can slide on to the rods. Initially all disks are stacked on the first tower, say tower A, such that no disk is placed over a smaller disk. The goal or objective is to move all these disks from tower A (first tower) to tower C (third tower). But you should obey the following rules. The rules of towers of hanoi puzzle are:

Java Program to Find Power of a Number

This is a java program to calculate power of a given number. The inputs are the number and its exponent (power). For example, if you give m and n, the result is m^n. You may use built-in function Math.pow() or hard code it.

Using Built-in Function

import java.util.Scanner;

public class Power{

public static void main(String[] args)
{
int m,n;
Scanner sc=new Scanner(System.in);
System.out.println("Enter number and its power");
m=sc.nextInt();
n=sc.nextInt();
System.out.printf("m^n = %.0f",(float)Math.pow(m,n));
}
}

Without using Built-in function

import java.util.Scanner;

public class Power{

public static void main(String[] args)
{
int m,n,i,p=1;
Scanner sc=new Scanner(System.in);
System.out.println("Enter number and its power");
m=sc.nextInt();
n=sc.nextInt();
for(i=0;i<n;i++)
    p*=m;
System.out.printf("m^n = %d",p);
}
}

Java Program For Matrix Multiplication

This is a java program for Matrix Multiplication. To understand how it works, you should first know how matrix multiplication is done mathematically.

import java.util.Scanner;

public class MatrixMult{

public static void main(String[] args)
{
int[][] m1=new int[10][10];
int[][] m2=new int[10][10];
int[][] prod=new int[10][10];
int i,j,k,r1,c1,r2,c2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter number of rows and columns of first matrix:");
r1=sc.nextInt();
c1=sc.nextInt();
System.out.println("Enter number of rows and columns of second matrix:");
r2=sc.nextInt();
c2=sc.nextInt();
if(r2==c1)
    {
    System.out.println("Enter elements of First matrix (row wise):");
    for(i=0;i<r1;i++)
        for(j=0;j<c1;j++)
            m1[i][j]=sc.nextInt();
    System.out.println("Matrix1 is :");
    for(i=0;i<r1;i++)
        {
        for(j=0;j<c1;j++)
            System.out.printf("%d ",m1[i][j]);
        System.out.printf("\n");
        }
    System.out.println("Enter elements of Second matrix (row wise):");
    for(i=0;i<r2;i++)
        for(j=0;j<c2;j++)
            m2[i][j]=sc.nextInt();
    System.out.println("Matrix2 is:");
    for(i=0;i<r2;i++)
        {
        for(j=0;j<c2;j++)
            System.out.printf("%d ",m2[i][j]);
        System.out.printf("\n");
        }
    System.out.println("Product of the Matrices (M1 x M2):");
    for(i=0;i<r1;i++)
        {
        for(j=0;j<c2;j++)
            {
            prod[i][j]=0;
            for(k=0;k<r1;k++)
                prod[i][j]+=m1[i][k]*m2[k][j];
            System.out.printf("%d ",prod[i][j]);
            }
        System.out.print("\n");
        }
    }
else
    {
    System.out.println("Matrices can't be multiplied.");
    System.out.print("No. of columns of first matrix and no of rows of second are different.");
    }
}
}

Output

Enter number of rows and columns of first matrix:
2
2
Enter number of rows and columns of second matrix:
2
2
Enter elements of First matrix (row wise):
5
8
6
4
Matrix1 is :
5 8 
6 4 
Enter elements of Second matrix (row wise):
5
6
8
9
Matrix2 is:
5 6 
8 9 
Product of the Matrices (M1 x M2):
89 102 
62 72

Java Program to Display Multiplication Tables of Given Number

This is a java program to display multiplication table of given number. For java program to display multiplication table of all numbers from 1 to 10, see this post: Program to display multiplication table of all numbers from 1 to 10

import java.util.Scanner;

public class Multiples{

public static void main(String[] args)
{
    int n, i;
    Scanner sc=new Scanner(System.in);
    System.out.printf("Enter the number:");
    n=sc.nextInt();
    for(i=1; i<=10; ++i)
        System.out.printf("%d * %d = %d \n", i, n, n*i);
}
}

Output:

Enter the number:5
1 * 5 = 5
2 * 5 = 10
3 * 5 = 15
4 * 5 = 20
5 * 5 = 25
6 * 5 = 30
7 * 5 = 35
8 * 5 = 40
9 * 5 = 45
10 * 5 = 50

Java Program to Display Multiplication Tables of All Number from 1 to 10

This is a java program to display multiplication tables of all number from 1 to 10. To see java program to display multiplication table of given number only, see this program:
Program to Display Multiplication Table of Given Number

public class Multiples{

public static void main(String[] args)
{
int i,j;
for(i=1;i<=10;i++)
    {
    for(j=1;j<=10;j++)
        System.out.printf("%d*%d=%d  ",i,j,i*j);
    System.out.printf("\n");
    }
}

}

Output:

1*1= 1 1*2= 2 1*3= 3 1*4= 4 1*5= 5 1*6= 6 1*7= 7 1*8= 8 1*9= 9 1*10=10
2*1= 2 2*2= 4 2*3= 6 2*4= 8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 2*10=20
3*1= 3 3*2= 6 3*3= 9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 3*10=30
4*1= 4 4*2= 8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 4*10=40
5*1= 5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 5*10=50
6*1= 6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 6*9=54 6*10=60
7*1= 7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 7*8=56 7*9=63 7*10=70
8*1= 8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64 8*9=72 8*10=80
9*1= 9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81 9*10=90
10*1=10 10*2=20 10*3=30 10*4=40 10*5=50 10*6=60 10*7=70 10*8=80 10*9=90 10*10=100

Java Program to Rotate Polygon - 2d Transformation Rotation in Java

This is a java program for rotation transformation in computer graphics. Rotation is one of the important 2d transformations in computer graphics. The program will tell you how to rotate points or polygon around a point (the pivot point). This CG lab program in java language reads the number of sides of polygon, co-ordinates of its vertices, the pivot point for rotation, and angle of rotation. It displays the original polygon and translated polygon in different colors in same screen. This program will tell you how to rotate a polygon in java. I override the paintComponent() method of JPanel to draw on a JPanel.

Java Program for Engine Piston Movement Animation

This program simulates the motion of the components of a two stroke engine. It shows the movement of piston, connecting rod and crank by animating them in java. The program override the paint method of a JFrame to simulate the piston movement in two stroke engine. This can be computer graphics lab (CG lab) problem. The program is as given below. The program uses sin and cos functions to simulate the crank. Also it uses the equation to find the distance between to points.

Decimal to BCD Converter in Java

In this post,we will see java program to convert decimal number to BCD representation. Binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four. Thus the decimal digit 1 corresponds to 0001, 2 corresponds to 0010,.... 8 corresponds to 1000 and 9 corresponds to 1001. Therefore, decimal number 194 can be represented in BCD as 0001 1001 0100. It should be noted that 1010, 1011, 1100, 1101,1110 and 1111 are illegal in BCD. The following java program converts any decimal number to BCD. But in this program, for conversion each digit in the decimal, we use Integer.toBinaryString() method. So, i have added another program which does not use this method.

Program 1:

    public static String toBCD(int num)
    {
        String BCD="";
        while(num!=0)
        {
        int t=num%10;
        String tBCD=Integer.toBinaryString(t);
        while(tBCD.length()<4)
            {
            tBCD="0"+tBCD;
            }
        BCD=tBCD+BCD;
        num/=10;
        }
        return BCD;
    }

Program 2:

import java.util.Scanner;
public class DecimalToBCD {

static String digitToBcd(int digit)
{
    String str="";
    for(int i=3;i>=0;i--)
        {
        int d=(int) Math.pow(2,i);
        if(digit/d!=0)
            {
                str+="1";
                digit-=d;
            }
        else
            str+="0";
        }
    return str;
}
    
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int decimal=sc.nextInt();
        int digit;
        String BCD="";
        while(decimal!=0)
            {
            digit=decimal%10;
            BCD=digitToBcd(digit)+" "+BCD;
            decimal/=10;
            }
        System.out.println("BCD is:"+BCD);
        
    }
}

The second program does not use any built in methods for conversion of decimal to BCD.

Java Program to Simulate Motion of Simple Pendulum

This is a java program to simulate motion of simple pendulum using java graphics. This was a problem given in computer graphics lab, which i was supposed to do using graphics.h header file in C. This is the java version of the same. If you are looking for a C Program, here it is: C Program to Simulate Simple Pendulum Motion - Computer Graphics Lab.

Output is as follows:

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;


public class JavaApplication1 extends JFrame{

    int pivotx,pivoty;
    double thetamax,theta;;
    double len=260;
    int x,y,ymax,xmax;
    int bobradius=30;
    int xsign=-1,ysign=1;
    double omega;
    
    public JavaApplication1()
    {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(600,400);
        thetamax=60*Math.PI/180;
        pivotx=getWidth()/2;
        pivoty=40;
        ymax=(int) (pivoty+len*Math.cos(thetamax));
        xmax=(int) (pivotx+len*Math.sin(thetamax));
        x=xmax;
        y=ymax;
        theta=thetamax;
        System.out.println("pivotx:"+pivotx+" pivoty:"+pivoty);
        System.out.println("starting x:"+x+ "y:"+y);
        System.out.println("starting theta="+theta);
        t.start();
    }

    @Override
    public void paint(Graphics g) {
        System.out.println("called");        
        g.setColor(Color.WHITE);
        g.fillRect(0, 0,getWidth(),getHeight());
        g.setColor(Color.red);
        g.fillOval(pivotx-4,pivoty-4,8,8);
        g.drawLine(pivotx,pivoty, x,y);
        g.fillOval(x-bobradius/2,y-bobradius/2,bobradius,bobradius);
        
    }
    
    Thread t=new Thread()
    {
      public void run()
      {
    try {
      while(true)
      {
      if(x>=pivotx+Math.abs(len*Math.sin(thetamax)))
        {
        System.out.println("right extreme");
        xsign=-1;
        ysign*=-1;
        x=xmax-1;
        Thread.sleep(40);
        }
      else if(x<=pivotx-Math.abs(len*Math.sin(thetamax)))
      {
          System.out.println("left extreme");
          ysign*=-1;
          xsign=1;
          x=(int) (pivotx-Math.abs(len*Math.sin(thetamax))+2);
          Thread.sleep(40);
      }
      else if(y>=pivoty+len)
        {
              ysign*=-1;
              System.out.println("mean position");
        }

      omega=y/60*Math.PI/180;
      double decr=xsign*omega;
          System.out.println("decrement:"+decr);
      theta=theta+decr;
      x=(int) (pivotx+len*Math.sin(theta));
      y=(int) (pivoty+len*Math.cos(theta));
          System.out.println("new theta:"+theta);
      repaint();
      Thread.sleep(40);
    
      }
            } catch (InterruptedException ex) {}
      }
    };
    
    
    public static void main(String[] args) {
        new JavaApplication1().setVisible(true);
    }
    
}

Simplest UDP Chat Program to Run on Single Computer in Java

This is a very simple UDP chat program using java with GUI (Graphical User Interface). The program uses DatagramPackets to send messages over network. Remember, this program only to be run on a single computer (for network simulation purpose). If you want a real UDP program that works on any network, see this post: Chat Room Application using UDP in Java
Program explanation is given below the program.

import java.io.*;
import javax.swing.*;
import java.net.*;
import java.awt.event.*;
import java.util.*;

public class UDPChat extends JFrame implements ActionListener
{
DatagramSocket ds;
JTextField txt;
JButton send;
JTextArea msgs;
int myport;
int destport;
DatagramPacket p;
byte[] b=new byte[200];

public UDPChat()
{
try{
try{
ds=new DatagramSocket(9999);
myport=9999;
p=new DatagramPacket(b,200);
ds.receive(p);
destport=p.getPort();
}catch(Exception ex)
{
ds=new DatagramSocket(0);
myport=ds.getLocalPort();
destport=9999;
String msg="hi";
p=new DatagramPacket(msg.getBytes(),msg.length(),InetAddress.getLocalHost(),destport);
ds.send(p);
}
setLayout(null);
txt=new JTextField();
send=new JButton("Send");
msgs=new JTextArea();
setSize(300,600);
add(txt);
txt.setSize(220,25);
txt.setLocation(5,5);
add(send);
send.setSize(70,25);
send.setLocation(230,5);
add(msgs);
msgs.setSize(300,530);
msgs.setLocation(0,70);
send.addActionListener(this);
receive.start();
}catch(Exception ex){ex.printStackTrace();}
}

public void actionPerformed(ActionEvent ae)
{
try{
DatagramPacket pkt=new DatagramPacket(txt.getText().getBytes(),txt.getText().length(),InetAddress.getLocalHost(),destport);
ds.send(pkt);
}catch(Exception e){e.printStackTrace();}
txt.setText("");
}

Thread receive=new Thread()
{
public void run()
{
try{
while(true)
 {
 DatagramPacket dp=new DatagramPacket(b,200);
 ds.receive(dp);
 msgs.setText(msgs.getText()+"\n"+new String(b));
 }
}catch(Exception exx){exx.printStackTrace();}
}
};

public static void main(String[] args)
{
UDPChat s=new UDPChat();
s.setVisible(true);
}

}

This simple program is enough to run as server or client. When the first user runs the application, it opens a DatagramSocket with port number 9999 (see line 22 in code). Since no Exception will be thrown from this line, it sets myport as 9999. Then waits to receive a DatagramPacket from the other user. When the packet is received, it takes destport from the received packet. Then starts adding GUI elements and then starts the thread to receive messages.

But when the second instance (client) of the program is run, line 22 in code throws a SocketException. Thus execution goes to the catch block. There it opens a DatagramSocket at some random port (ephemeral port assigned by OS). Then, sends a packet to port 9999 in the same PC. This time the first instance (server) is still waiting for a packet as said earlier. It receives this DatagramPacket sent by client a gets its destination port. The client's destport is 9999, as it knew it is already occupied by the SocketException.

The sending of message is carried out when send button is clicked. We use an ActionListener for that. The method public void actionPerformed(ActionEvent ae) is invoked whenever the button is clicked.

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Using Built-in Function

Without using Built-in function

Output

Output:

Output:

Program 1:

Program 2: