Question

Write a Java application with a main() to find the two largest distinct integers entered on the command line by the user. We are just creating a simple stand-alone application. All your code can be in main().

Answer 1

Answer:

import java.util.Scanner; // Scanner class is to use input output functions

public class TwoDistinctLargest //class to find two distinct largest nos

{

public static void main(String[] args) { //start of main() function

Scanner input = new Scanner(System.in); // creates Scanner type object

       int integers = 0, largest1 = 0, largest2 = 0; // declare variables

/* integers holds the input integer values, largest1 has 1st largest number and largest 2 contains second distinct largest number, i is used as the count variable to move through the input integers */

       int i = 0;  

//prompts user to enter integers and enter 0 to stop

       System.out.println("Enter the integers (press 0 to stop): ");

       integers = input.nextInt(); //reads and scans input integers

       while(integers != 0) {

/* the loop keeps taking integer values from user until the value of integers is equal to 0, this means until the user enters 0 */

//checks if the value of integer is greater than first largest computed number

           if(integers > largest1) {

//if the value in largest1 is greater than that of largest2

               if(largest1 > largest2) {

                   largest2 = largest1; } // then value of largest1 is set to largest2                

               largest1 = integers; // largest1 now holds the value of integers //which means largest1 holds the first distinct largest integer

           } else { //checks if the value of integers is greater than largest2

               if(integers > largest2) {

//if the value of integers is not equal to that of largest1

                   if(integers!=largest1)  {

// set the value of second distinct largest number to largest2

                   largest2 = integers;}              }            }

                     i++; //keeps moving to the next input integer

           integers = input.nextInt();     //keeps taking input integers    }      

//prints the two distinct largest integers

       System.out.println("\n The 1st largest distinct integer is " + largest1);

       System.out.println("\n The 2nd largest distinct integer is " + largest2); } }

Explanation:

Lets suppose the user inputs the following integers

1, 6, 5, 6, 0

Initial values are:

integers = 0

largest1 = 0

largest2 = 0

i = 0

When the user enters 1, then value of integers = 1

while loop checks if integers!=0. As integers =1 so the program enters the body of while loop. The first IF condition is checked if(integers > largest1)

As largest1 = 0 and integers =1 so this condition evaluates to true as 1 > 0

So the statements in the body of this IF condition are executed. This if conditions contains another if statement if(largest1 > largest2) which checks if the value largest1 is greater than that of largest2. Its false because largest1 =0 and largest2 =0 so largest1 = largest2, so the statement of this if condition body will not execute and program moves to this                 largest1 = integers; statement which sets the value of integers i.e. 1 to largest1. So the value of largest1 = 1

Now the i is incremented by 1 and it points at second value of integers= 6.

while loop checks if integers!=0. As integers =6 so the program enters the body of while loop. The first IF condition is checked if(integers > largest1)

As largest1 = 1 and integers =6 so this condition evaluates to true as 6>1

So the statements in the body of this IF condition are executed. This if conditions contains another if statement if(largest1 > largest2) which checks if the value largest1 is greater than that of largest2.

Its true because largest1 =1 and largest2 =0 so largest1 > largest2, so the next statement is executed largest2 = largest1; So now the value of largest2=1.

Now program moves to this largest1 = integers; statement which sets the value of integers i.e. 6 to largest1. So the value of largest1 = 6

Now the i is incremented by 1 and it points at second value of integers= 5.

while loop condition is again true. IF condition is checked if(integers > largest1)

As largest1 = 6 and integers =5 so this condition evaluates to false as 5<6. So this IF part will not execute and program control moves to the else part.

Else part has an if condition if(integers > largest2) which evaluates to true because integers = 5 and largest2 = 1 so the program moves to next if statement inside the previous if statement of else part i.e. if(integers!=largest1). This if statement is the main statement which will help in finding two distinct largest numbers in case the same largest value is input more than once. It checks If the value of integers is not equal to largest1 value. As integers = 5 and  largest1 = 6 so this if condition is true. If this condition is not used in this program then largest2 will not be assigned distinct largest values but assigned 6 for both largest1 and largest2 as 6 is input twice. Next this if statement  largest2 = integers assigns value of integers to largest2 which is the second largest distinct integer.

Now the i is incremented by 1 integers value become 0.

while loop checks if integers!=0. As integers =0 so the while loop breaks. The last two print statements which produce following output.

The 1st largest distinct integer is: 6

The 2nd largest distinct integer is: 5