COMPUTER PROGRAMMING I 2013 WEEK 4

STATIC METHODS

EXERCISES (EXERCISE problems are for your understanding the topic. Will not return as homework)

In order to understand the topics, write down exercise problems and see that they are working properly, this will give you the backgroud to solve the homework problems. You are required to return only the homework problem codes and solutions. In exam, some of the example or homework problems will be asked as questions, so be sure you understand all of them properly.

IF STATEMENT

import javax.swing.*;

class W4E1

{ public static String action(String weather)

{

String s;

if(weather.equals("clear"))

{s="go for walking in the park";}

else if(weather.equals("rainy"))

{s="study computer programming I";}

else if(weather.equals("cloudy"))

{s="go to the movie theater";}

else

{s="Weather condition is not given";}

return s;

}

public static void print(String s,String s1)

{JOptionPane.showMessageDialog(null,s,s1,JOptionPane.PLAIN_MESSAGE);}

public static void main(String args[])

{ String weather;

weather=JOptionPane.showInputDialog("wheather condition: clear/rainy/cloudy");

print(action(weather),"======If statement======");

}

}

class W4E1A

{

public static void main(String args[])

{ String weather;

weather=JOptionPane.showInputDialog("wheather condition: clear/rainy/cloudy");

String s=W4E1.action(weather);

String s1="======If statement======";

W4E1.print(s,s1);

}

}

import javax.swing.*;

class W4E2

{ public static String action(int n)

{ String s="";

if(n==1)

{s="go for walking in the park";}

else if(n==2)

{s="study computer programming I";}

else if(n==3)

{s="go to the movie theater";}

else

{s="Weather condition is not given";}

return s;

}

public static void main(String args[])

{ String weather;

weather=JOptionPane.showInputDialog("wheather condition:\n 1:clear\n 2:rainy\n 3:cloudy");

W4E1.print(action(Integer.parseInt(weather)),"======If statement======");

}

}

import javax.swing.*;

class W4E2A

{

public static void main(String args[])

{ String weather;

weather=JOptionPane.showInputDialog("wheather condition:\n 1:clear\n 2:rainy\n 3:cloudy");

String w=W4E2.action(Integer.parseInt(weather));

W4E1.print(w,"======If statement======");

}

}

import javax.swing.*;

public class W4E3

{

public static double determinant(double a,double b,double c)

{return b*b-4.0*a*c; }

public static String root_type(double det)

{ boolean b1=det>0;

boolean b2=det<0;

boolean b3=det==0;

String s="";

if(b1)

{s+="determinant greater than 0 \nthe roots are real";}

else if(b2)

{s+="determinant smaller than 0\nthe roots are complex";}

else

{s+="determinant are equal to 0\ntwo equal real roots";}

return s;

}

public static void main(String arg[])

{ //Calculate d=b*b-4.0*a*c;

String sa=JOptionPane.showInputDialog("a=");

String sb=JOptionPane.showInputDialog("b=");

String sc=JOptionPane.showInputDialog("c=");

double a=Double.parseDouble(sa);

double b=Double.parseDouble(sb);

double c=Double.parseDouble(sc);

//Determinant

double d=determinant(a,b,c);

JOptionPane.showMessageDialog(null,root_type(d));

}

}

import javax.swing.*;

public class W4E3A

{

public static double read(String s)

{String sa=JOptionPane.showInputDialog(s);

double a=Double.parseDouble(sa);

return a;

}

public static void main(String arg[])

{ //Calculate d=b*b-4.0*a*c;

double a=read("a=");

double b=read("b=");

double c=read("c=");

//Determinant

double d=W4E3.determinant(a,b,c);

String s="determinant = "+d+"\n"+W4E3.root_type(d);

String s1="root type of quadratic equation";

W4E1.print(s,s1);

}

}

Note that this program checks out if the given string is an integer, if it is not an integer it will give the error message “the given input is not an integer"

import javax.swing.*;

class W4E4

{ public static int toInt(String s)

{String s2="^-?[0-9]+(\\.[0-9]+)?$";

boolean b=s.matches(s2);

int n=0;

if(b) {n=Integer.parseInt(s);}

else {W4E1.print("the given input is not an integer 0 returned","ERROR MESSAGE");}

return n;

}

public static void main(String args[])

{ String weather;

weather=JOptionPane.showInputDialog("wheather condition:\n 1:clear\n 2:rainy\n 3:cloudy");

W4E1.print(W4E2.action(toInt(weather)),"======If statement======");

}

}

import javax.swing.*;

class W4E4A

{ public static String read(String s)

{String sa=JOptionPane.showInputDialog(s);

return sa;

}

public static void main(String args[])

{ String weather;

weather=read("wheather condition:\n 1:clear\n 2:rainy\n 3:cloudy");

W4E1.print(W4E2.action(W4E4.toInt(weather)),"======If statement======");

}

}

Note that this program checks out if the given string is a double number, if it is not a double it will give the error message “the given input is not a double number ". Do not wory about the content of the comparison string for now, just use it as it is.

import javax.swing.*;

class W4E5

{ public static double toDouble(String s)

{String s2="[\\x00-\\x20]*[+-]?(((((\\p{Digit}+)(\\.)?((\\p{Digit}+)?)([eE][+-]?(\\p{Digit}+))?)|(\\.((\\p{Digit}+))([eE][+-]?(\\p{Digit}+))?)|(((0[xX](\\p{XDigit}+)(\\.)?)|(0[xX](\\p{XDigit}+)?(\\.)(\\p{XDigit}+)))[pP][+-]?(\\p{Digit}+)))[fFdD]?))[\\x00-\\x20]*";

boolean b=s.matches(s2);

double n=0.0;

if(b) {n=Double.parseDouble(s);}

else {W4E1.print("the given input is not a double 0 returned","ERROR MESSAGE");}

return n;

}

public static void main(String args[])

{ String s1;

s1=JOptionPane.showInputDialog("enter a double number : ");

double x=toDouble(s1);

String s="the given double number is "+x;

JOptionPane.showMessageDialog(null,s,"======If statement in static method======",JOptionPane.PLAIN_MESSAGE);

}

}

import javax.swing.*;

class W4E5A

{

public static void main(String args[])

{ String s1;

s1=W4E4A.read("enter a double number : ");

double x=W4E5.toDouble(s1);

String s="the given double number is "+x;

JOptionPane.showMessageDialog(null,s,"======If statement in static method======",JOptionPane.PLAIN_MESSAGE);

}

}

WHILE STATEMENT

import javax.swing.*;

class W4E6

{ public static String func(int x1,int x2)

{ int y;

String s="";

int x=x1;

while(x<=x2)

{y=x*x+2*x+1;

s+="x = "+x+" y = "+y+"\n";

x++;

}

return s;

}

public static void main(String args[])

{ int x1=0;

int x2=20;

JOptionPane.showMessageDialog(null,func(x1,x2),"====== function evaluation ======",JOptionPane.PLAIN_MESSAGE);

}

}

import javax.swing.*;

class W4E6A

{ public static int read(String s)

{String sa=JOptionPane.showInputDialog(s);

int a=Integer.parseInt(sa);

return a;

}

public static void main(String args[])

{ int x1=read("x1=");

int x2=read("x2=");

String s=W4E6.func(x1,x2);

String s1="====== function evaluation ======";

W4E1.print(s,s1);

}

}

import javax.swing.*;

class W4E7

{ public static int sum(int x1,int x2)

{ int sum=0;

int x=x1;

while(x<x2)

{sum+=x;

x++;

}

return sum;

}

public static void main(String args[])

{ //sum of the numbers from 1 to 20

int a1=1;

int a2=20;

String s="";

s+=" sum = "+sum(a1,a2)+"\n";

W4E1.print(s,"====== function evaluation ======");

}

}

import javax.swing.*;

class W4E7A

{

public static void main(String args[])

{ //sum of the numbers from 1 to 20

int a1=W4E6A.read("x1=");

int a2=W4E6A.read("x2=");

String s="";

s+=" sum = "+W4E7.sum(a1,a2)+"\n";

W4E1.print(s,"====== function evaluation ======");

}

}

import javax.swing.*;

class W4E8

{ public static int func(int x)

{return x*x+2*x+1;}

public static String plot(int x1,int x2)

{ int y=0;

String s="";

String star="*";

String space=" ";

String sum;

int x=x1;

while(x<=x2)

{ y=func(x); // function to be plotted

int i=0;

sum=star;

while(i<y)

{ sum = space+sum;

i++;

}

s+=sum+"\n";

x++;

}

return s;

}

public static void main(String args[])

{ int x1=-10;

int x2=10;

W4E1.print(plot(x1,x2),"====== function plot ======");

}

}

import javax.swing.*;

class W4E8A

{

public static void main(String args[])

{ int x1=W4E6A.read("x1=");

int x2=W4E6A.read("x2=");

W4E1.print(W4E8.plot(x1,x2),"====== function plot ======");

}

}

In the next example a more series will be calculated

note that e=2.7182818…

import javax.swing.*;

public class W4E9

{ public static double exp(double x)

{ // number e = 2.718...

// exp(x) = 1 + x /1! + x2 / 2! + x3 / 3! + x4 / 4! + .double power=1;

double exponent=1;

double factorial=1;

int number=1;

double power=1;

while(number<=300)

{

factorial*=number;

power*=x;

exponent+=power/factorial;

number++;

}

return exponent;

}

// main method begins execution of Java application

public static void main( String args[] )

{

String sa=JOptionPane.showInputDialog("x=");

double x = Double.parseDouble(sa);

String s="exp("+x+") = "+exp(x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class

public class W4E9A

{

// main method begins execution of Java application

public static void main( String args[] )

{

double x = W4E3A.read("x=");

String s="exp("+x+") = "+W4E9.exp(x)+"\nMath library :"+Math.exp(x);

W4E1.print(s,"exp");

} // end method main

} // end of class

A series Formula for ln(x) is given by

write program to calculate series by using a while loop.. Note that equation can be further simplify if a second conversion z=y*y is made

note that ln(2.718281)=1.0

import javax.swing.*;

public class W4E10

{ public static double log(double x)

{double y=(x-1.0)/(x+1.0);

double power=2.0*y;

double z=y*y;

int n=0;

double ln=0;

while(n<=300)

{

ln+=1./(2.0*n+1.0)*power;

power*=z;

n++;

}

return ln;

}

// main method begins execution of Java application

public static void main( String args[] )

{ // ln(x) x>0

String sa=JOptionPane.showInputDialog("x = ");

double x = Double.parseDouble(sa);

String s="ln("+x+") = "+log(x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class BPIH4E1

import javax.swing.*;

public class W4E10A

{

// main method begins execution of Java application

public static void main( String args[] )

{

double x = W4E3A.read("x=");

String s="log("+x+") = "+W4E10.log(x)+"\nMath library :"+Math.log(x);

W4E1.print(s,"exp");

} // end method main

} // end of class

(This program combines two previous programs to calculate power function

import javax.swing.*;

public class W4E11

{ public static double pow(double a,double x)

{ return W4E9.exp(x*W4E10.log(a));

}

public static void main( String args[] )

{ // a^x x>0

String sa=JOptionPane.showInputDialog("a = ");

double a = Double.parseDouble(sa);

String sx=JOptionPane.showInputDialog("x = ");

double x = Double.parseDouble(sx);

String s=a+"^"+x+" = "+pow(a,x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class

import javax.swing.*;

public class W4E11A

{

public static void main( String args[] )

{ // a^x x>0

double a = W4E3A.read("a = ");

double x = W4E3A.read("x = ");

String s=a+"^"+x+" = "+W4E11.pow(a,x)+"\nMath library :"+Math.pow(a,x);

W4E1.print(s,"pow");

} // end method main

} // end class

FOR STATEMENT

import javax.swing.*;

class W4E12

{ public static String func(int x1,int x2)

{ int y;

String s="";

for(int x=x1;x<x2;x++)

{y=x*x+2*x+1;

s+="x = "+x+" y = "+y+"\n";

}

return s;

}

public static void main(String args[])

{ int x1=0;

int x2=20;

JOptionPane.showMessageDialog(null,func(x1,x2),"====== function evaluation ======",JOptionPane.PLAIN_MESSAGE);

}

}

import javax.swing.*;

class W4E13

{ public static int sum(int x1,int x2)

{ int sum=0;

for(int x=x1;x<x2;x++)

{sum+=x;}

return sum;

}

public static void main(String args[])

{ //sum of the numbers from 1 to 20

int x1=1;

int x2=20;

String s="";

s+=" sum = "+sum(x1,x2)+"\n";

JOptionPane.showMessageDialog(null,s,"====== function evaluation ======",JOptionPane.PLAIN_MESSAGE);

}

}

import javax.swing.*;

class W4E14

{ public static int func(int x)

{return x*x+2*x+1;}

public static String plot(int x1,int x2)

{ int y=0;

String s="";

String star="*";

String space=" ";

String sum;

for(int x=x1;x<=x2;x++)

{ y=func(x); // function to be plotted

int i=0;

sum=star;

while(i<y)

{ sum = space+sum;

i++;

}

s+=sum+"\n";

}

return s;

}

public static void main(String args[])

{ int x1=-10;

int x2=10;

W4E1.print(plot(x1,x2),"====== function plot ======");

}

}

In this program Math library function Math.exp(x) is also used to compare the results

import javax.swing.*;

public class W4E15

{ public static double exp(double x)

{ // number e = 2.718...

// exp(x) = 1 + x /1! + x2 / 2! + x3 / 3! + x4 / 4! + .double power=1;

double exponent=1;

double factorial=1;

int number=1;

double power=1;

while(number<=300)

{

factorial*=number;

power*=x;

exponent+=power/factorial;

number++;

}

return exponent;

}

// main method begins execution of Java application

public static void main( String args[] )

{

String sa=JOptionPane.showInputDialog("x=");

double x = Double.parseDouble(sa);

String s="exp("+x+") = "+exp(x)+" Math library value = "+Math.exp(x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class

A series Formula for ln(x) is given by

write program to calculate series by using a for loop.. Note that equation can be further simplify if a second conversion z=y*y is made

In this program Math library function Math.log(x) is also used to compare the results

import javax.swing.*;

public class W4E16

{ public static double log(double x)

{ // number e = 2.718...

// ln(e) = 1

double y=(x-1.0)/(x+1.0);

double power=2.0*y;

double z=y*y;

int n=0;

double ln=0;

while(n<=300)

{

ln+=1./(2.0*n+1.0)*power;

power*=z;

n++;

}

return ln;

}

// main method begins execution of Java application

public static void main( String args[] )

{

String sa=JOptionPane.showInputDialog("x=");

double x = Double.parseDouble(sa);

String s="exp("+x+") = "+log(x)+" Math library value = "+Math.log(x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class

In this program Math library function Math.pow(x) is also used to compare the results

import javax.swing.*;

public class W4E17

{ public static double pow(double a,double x)

{ return W4E15.exp(x*W4E16.log(a));

}

public static void main( String args[] )

{ // a^x x>0

String sa=JOptionPane.showInputDialog("a = ");

double a = Double.parseDouble(sa);

String sx=JOptionPane.showInputDialog("x = ");

double x = Double.parseDouble(sx);

String s=a+"^"+x+" = "+pow(a,x)+" Math library value = "+Math.pow(a,x);

JOptionPane.showMessageDialog(null,s);

} // end method main

} // end class

import javax.swing.*;

public class W4E17A

{

public static void main( String args[] )

{ // a^x x>0

double a = W4E3A.read("a = ");

double x = W4E3A.read("x = ");

String s=a+"^"+x+" = "+W4E17.pow(a,x)+"\nMath library :"+Math.pow(a,x);

W4E1.print(s,"pow");

} // end method main

} // end class

class W4E18

{ public static String unicode(char x1,char x2)

{String s="";

int i=1;

for(char b=x1;b<=x2;b++)

{s+=b+" ";if(i%10==0) s+="\n";i++;}

return s;

}

public static void main(String args[])

{

char c1='\u2200';

char c2='\u22F1';

JOptionPane.showMessageDialog(null,unicode(c1,c2),"======Unicode Letters======",JOptionPane.PLAIN_MESSAGE);

}

}

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. Following example finds prime numbers.

import javax.swing.*;

class prime4

{ public static String prime(int n1,int n2)

{

int i,j;

String s=" ";

for(i=n1;i<=n2;i++)

{for(j=2;j<i && (i%j)!=0;j++) {}

if(i==j) {s+=i+"\n";}

}

return s;

}

public static void main(String args[])

{

int n1=Integer.parseInt(JOptionPane.showInputDialog("enter first number : "));

int n2=Integer.parseInt(JOptionPane.showInputDialog("enter second number : "));

JOptionPane.showMessageDialog(null,prime(n1,n2),"Prime numbers between "+n1+" and "+n2,JOptionPane.PLAIN_MESSAGE);

}

}

HOMEWORKS (You will return solutions of this sets as homework)

Utilise static methods for each homework problem

HW1 : Enter the season as a String variable, if it is fall write down “it is the season of golden trees” , if it is winter write down “it is the season of skiing”, if it is spring write down “it is the season of rebirth of the natüre”, and if it is summer write down “it is the golden summer”

HW 2: write a program to calculate factorial of an integer number (multiplication of numbers 1 to n)

n!=1*2*3*4..*n.

a) Use while loop

b) Use for loop

(you will write two version of the program first with a while loop, second with a for loop)

HW 3 : When a complex numbers such as p=3.141592653589793, series solution is used. A series

can be used. Write a static method

public static double PI() to calculate the given series by using a while loop.

HW 4: When a function such as sinh is required to calculate by computer, series solution is used. A series

can be used to calculate such a function. Write a static method public static double sinh(double x) to calculate the

given series by using a for loop.

Note: you can check your result by using Math.sinh(x) library static method.