Question

In java please.

SumOfPowerOfTwo

The following program can be done in a single class.

Write a program that requests and reads in a integer number between 1 and 40 inclusively. Repeat the loop until a proper number is entered.

Call the method powersOfTwoSum with the number as the actual parameter. Expect a value of type long as a return value.

powersOfTwoSum(int number)

This method must use a recursive technique to return the sum of the powers of two from the number down to zero. For example, if the input is 5 the return value would be:

2⁵ + 2⁴ + 2³ + 2² + 2¹ +1

Two Samples:

Enter an integer between 1 and 20 inclusively: 2

The sum of the powers of two from 0 to 2 is 7

Enter an integer between 1 and 40 inclusively: 40

The sum of the powers of two from 0 to 40 is 2199023255551

Answer 1

The answer to this question is as follows:

The code I provided should work is as follows:

for 2 the output is 7 because 20+21+22=1+2+4=7

for 5 the output is 63 because of 20+21+22+23+24+25=1+2+4+8+16+32=63

import java.util.*;
public class MyClass {
long powersOfTwoSum(int num)
{
int sum=(int)(Math.pow(2,num));
if(num==0)
{
return 1;
}
else
return powersOfTwoSum((num-1))+sum;
}
  
public static void main(String args[]) {
int num;
Scanner sc=new Scanner(System.in);
num=sc.nextInt();
while(true)
{
if(num>=1 && num<=40)
{
break;
}
else
{
System.out.println("Enter an integer between 1 and 20 inclusively:");
num=sc.nextInt();
}
}
MyClass m=new MyClass();
System.out.println(m.powersOfTwoSum(num));
}
}