# Raising a number to the power. Help!

macca Mason

Greenhorn

Posts: 13

posted 12 years ago

Hi I am stuck. I need to make a program that allows me to raise a number to the power.

The initial number is entered by the user as so is the power value.

Hi am new to programming so be descriptive in your replies.

Please help me. I have been stuck for ages.

Thx

[ December 02, 2003: Message edited by: macca Mason ]

The initial number is entered by the user as so is the power value.

Hi am new to programming so be descriptive in your replies.

Please help me. I have been stuck for ages.

Thx

[ December 02, 2003: Message edited by: macca Mason ]

chi Lin

Ranch Hand

Posts: 348

chi Lin

Ranch Hand

Posts: 348

posted 12 years ago

java.lang package is imported automatically,

you could just use Math.pow() for calculation.

If you need to use some package that is not automatically imported

do somthing like

java.util package.

[ December 02, 2003: Message edited by: chi Lin ]

you could just use Math.pow() for calculation.

If you need to use some package that is not automatically imported

do somthing like

**import java.util.*;**to import classes underjava.util package.

[ December 02, 2003: Message edited by: chi Lin ]

not so smart guy still curious to learn new stuff every now and then

Dirk Schreckmann

Sheriff

Posts: 7023

posted 12 years ago

Also, macca, since you're new to programming and since your power value is an int, if loops aren't foreign to your understanding, you might want to implement this program without using the Math.pow() method. You can do it with a pretty simple for-loop.

If you've further questions, just ask.

If you've further questions, just ask.

macca Mason

Greenhorn

Posts: 13

posted 12 years ago

Still got problem with my powers program can you please help!

Thanks

/*

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:20: '.class' expected

Math.pow(double,double)

^

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:22: ')' expected

System.out.println("The result of powers is "+ results);

^

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:20: unexpected type

required: value

found : class

Math.pow(double,double)

^

3 errors

Tool completed with exit code 1

*/

Thanks

/*

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:20: '.class' expected

Math.pow(double,double)

^

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:22: ')' expected

System.out.println("The result of powers is "+ results);

^

C:\Documents and Settings\Mahmoud Maguid\My Documents\JavaCode\Coursework\Powers.java:20: unexpected type

required: value

found : class

Math.pow(double,double)

^

3 errors

Tool completed with exit code 1

*/

posted 12 years ago

The error messages are not very helpful at all, are they? The problem is on the line

result = Math.pow(double, double);

"double" is a type, not a variable name; you want to pass the name of some double variables:

result = Math.pow(number, power);

But you haven't initialized any appropriate variables yet, so you've got a ways to go.

Before you start with loops and things, maybe you could get a simpler program working that just printed out, say 2 to the 2nd power and verified that you got "4". Then move on from there.

result = Math.pow(double, double);

"double" is a type, not a variable name; you want to pass the name of some double variables:

result = Math.pow(number, power);

But you haven't initialized any appropriate variables yet, so you've got a ways to go.

Before you start with loops and things, maybe you could get a simpler program working that just printed out, say 2 to the 2nd power and verified that you got "4". Then move on from there.

macca Mason

Greenhorn

Posts: 13

posted 12 years ago

Macca,

The main method must have the following signature:

It is required to return void (not double)

The main method must have the following signature:

It is required to return void (not double)

[OCA 8 book] [OCP 8 book] [Blog] [JavaRanch FAQ] [How To Ask Questions The Smart Way] [Book Promos]

Other Certs: SCEA Part 1, Part 2 & 3, Core Spring 3, TOGAF part 1 and part 2

macca Mason

Greenhorn

Posts: 13

posted 12 years ago

I have canceled the math.pow statement but used the for loop instead

Can you please show me some directions to go.

I belive the main problem is storing the power number so it can loop again

[ edited to improve code formatting for greater readability -ds ]

[ December 08, 2003: Message edited by: Dirk Schreckmann ]

Can you please show me some directions to go.

I belive the main problem is storing the power number so it can loop again

[ edited to improve code formatting for greater readability -ds ]

[ December 08, 2003: Message edited by: Dirk Schreckmann ]

Langdon Algar

Greenhorn

Posts: 1

posted 12 years ago

Macca,

Hi there, I am fairly new to Java as well, a way to do your

problem while using "int"s provided by the user and the "Math.pow" method

which takes "double"s would be to convert the ints to doubles and then send

them to the Math.pow method. As in the following:

-----------------------------------------------------------------

public class Powers {

public static void main(String[] args) {

if (args.length <2) {

System.out.println("enter two numbers on the command line");

} else {

int number1 = Integer.parseInt(args[0]);

int power1 = Integer.parseInt(args[1]);

int answer2;

double answer1;

double number2 = (double) number1;

double power2 = (double) power1;

answer1 = Math.pow(number2, power2);

answer2 = (int) answer1;

System.out.println(number1 + " to the " + power1 + " power is: " + answer2);

}

}

}

----------------------------------------------

Hope this helps,

Langdon

Hi there, I am fairly new to Java as well, a way to do your

problem while using "int"s provided by the user and the "Math.pow" method

which takes "double"s would be to convert the ints to doubles and then send

them to the Math.pow method. As in the following:

-----------------------------------------------------------------

public class Powers {

public static void main(String[] args) {

if (args.length <2) {

System.out.println("enter two numbers on the command line");

} else {

int number1 = Integer.parseInt(args[0]);

int power1 = Integer.parseInt(args[1]);

int answer2;

double answer1;

double number2 = (double) number1;

double power2 = (double) power1;

answer1 = Math.pow(number2, power2);

answer2 = (int) answer1;

System.out.println(number1 + " to the " + power1 + " power is: " + answer2);

}

}

}

----------------------------------------------

Hope this helps,

Langdon

Dirk Schreckmann

Sheriff

Posts: 7023

posted 12 years ago

Considering your power method...

Why are you checking to see if

Let me be blunt. Your for-loop is completely wrong. Also, your power method doesn't have enough information to perform such an operation properly. Remember, the power function requires two operands - one which I'll call the base number and the other which is the power to which the base number is to be raised.

Think for a moment about the power function, and perhaps the pattern of a proper for-loop shall become clearer.

What happens when we raise a number, x, to 2? Simple. Multiply x by itself one time - x * x.

What happens when we raise a number, x, to 3? Again, simple. Multiply x by itself two times - x * x * x.

What happens when we raise a number, x, to 4? Multiply x by itself three times - x * x * x * x.

And What happens when we raise a number, x, to the number, n? Well, multiply x by itself n - 1 times is likely the pattern that has revealed itself.

So, is the solution becoming clearer?

Why are you checking to see if

*initialnum == initialnum*? A mathematician would likely know for sure, but I think that it's the identity theorem that always makes such an expression true - a number always equals itself. So, this will always evaluate to be true.Let me be blunt. Your for-loop is completely wrong. Also, your power method doesn't have enough information to perform such an operation properly. Remember, the power function requires two operands - one which I'll call the base number and the other which is the power to which the base number is to be raised.

Think for a moment about the power function, and perhaps the pattern of a proper for-loop shall become clearer.

What happens when we raise a number, x, to 2? Simple. Multiply x by itself one time - x * x.

What happens when we raise a number, x, to 3? Again, simple. Multiply x by itself two times - x * x * x.

What happens when we raise a number, x, to 4? Multiply x by itself three times - x * x * x * x.

And What happens when we raise a number, x, to the number, n? Well, multiply x by itself n - 1 times is likely the pattern that has revealed itself.

So, is the solution becoming clearer?