Write a Java program that prompts the user to enter a number and prints all the positive integer powers of 2 less than or equal that number.

Question

Do not use the method Math.pow() in your solution.
E.g., if the user enters 9, the output should be:
2 to the power 0 = 1
2 to the power 1 = 2
2 to the power 2 = 4
2 to the power 3 = 8

Answer 1

import java.io.*;

class Power2

{

private int N;

Console console;

Power2()

{

console = System.console();

N=0;

}

public void Go()

{

String inbuff;

int pow2 = 1;

try

{

N=0;

while (N<1)

{

System.out.print(" Please input a positive integer :> ");

inbuff = console.readLine();

N = Integer.parseInt(inbuff);

}

int expo=0;

while (pow2<=N)

{

System.out.println(" 2 to the power of " + expo + " is " + pow2);

expo++; pow2 *=2;

}

} //try

catch (Exception ex)

{

System.out.println(" An input error has occured ");

}

} //Go

public static void main(String args[])

{

Power2 myPower2 = new Power2();

myPower2.Go();

} //main

} //class