Loop Controls

Here is an example of range validation, but has no control as how many times the user can take to input the correct value

Example-1: Input Validation

package com.example;
import javax.swing.*;
public class loopContinued
{
public static void main(String[] args)
{
//input validation
String input;
int number;
input= JOptionPane.showInputDialog(“Please enter a number” +
“between 1 and 100”);
number=Integer.parseInt(input);
// now let us validate
while(number <1 || number >100) // OR operator to check outside range
{
JOptionPane.showMessageDialog(null,
“Not a valid number”);
input=JOptionPane.showInputDialog(“Please enter a number between 1 and 100”);
number = Integer.parseInt(input);

}
}
}

Example-2:  user control of Loop

In the example below, we use control the loop variable

package com.example;
import javax.swing.*;
public class loopContinued
{
public static void main(String[] args)
{
//input validation

String input;

int Maxnumber;
input=JOptionPane.showInputDialog(“How high should I go to square the number”);
Maxnumber = Integer.parseInt(input);
System.out.println(“number Squareed “);

for(int i=1; i<= Maxnumber; i++)
{

System.out.println( i + “\t\t\t\t” + i*i);

}

}s

}

3rd Example:

Running total, is the summing the number to the previous total. Let us see through the example

In this example, system ask the user how many days sale data is available, then he is prompted to daily sales data and calculates the running total.

Also in the example we will use formatted output. For that, we use the class DecimalFormat

We use within quottes ## .. and 00

DecimalFormat Dollar=new DecimalFormat(“#,##0.00”)

this means if there is something belo #; show it else don’t show

If there is something belo 0, show it else show 0. On the decimal side if there are 2 zeros, show upto 2-decimal places. Number or zeros after decimal point will be digits after (.). See declaration and useage in showMessageDialog();

package com.example;
import javax.swing.*;
public class loopContinued
{
public static void main(String[] args)
{
//input validation
String input;

int days; // ask user to give how many days data is required
double sales;//ask use to give daily sales
double totalSales=0.0; // keep record or running total

DecimalFormat Dollar =new DecimalFormat(“#,##0.00”);

input=JOptionPane.showInputDialog(“please input number of days the sales availble?”);
days = Integer.parseInt(input);
for(int count =0; count<days; count++)

{

input=JOptionPane.showInputDialog(“Enter sales for the day”+(count+1));
sales=Double.parseDouble(input);
totalSales += sales;

}
JOptionPane.showMessageDialog(null, “Total sale is: “+Dollar.format(totalSales));

System.exit(0);

}

}

Example-4: Sentinal values

A sentinal values can be used to  notify  program to stop acquireing inputs.

Ask user to input a value. Then we double for the user multiplying by 2.

Please enter value to double untill he chooses to stop.

package com.example;
import javax.swing.*;
public class loopContinued
{
public static void main(String[] args)
{
//input validation
String input;

int value;
int doubleValue;
input=JOptionPane.showInputDialog(“Please enter a value to double” +
“0 to stop”);
value=Integer.parseInt(input);
while(value!=0)

{

doubleValue= value * 2;
JOptionPane.showMessageDialog(null, “”+ value + “doubled is”+doubleValue);
input=JOptionPane.showInputDialog(“Please enter a value to double” +
“0 to stop”);
value=Integer.parseInt(input);

}

System.exit(0);

}

}