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Java Tutorial: The Power Function

Xah Lee, 2005-01

It's interesting that java doesn't provide the power operator. (e.g. “^” in 3^4). You have to use java.lang.Math.pow(3,4). That method returns type “double”.

import java.lang.Math;

class t2 {
    public double square (int n) {
        return java.lang.Math.pow(n,2);
    }
}

class t1 {
    public static void main(String[] arg) {
        t2 x1 = new t2();
        double m = x1.square(3);
        System.out.println(m);
    }
}

In the above example, we defined a class “t2” and “t1”.

t1 is the main class for this file. The file name thus should be 〔t1.java〕. The t2 is a auxiliary class, that is, a helper class for what we need do in this package.

The t2 class defines one method, the “square”. It takes a “integer” and returns a decimal number of type “double”. (“double” is basically a decimal number normal length the computer can store.)

In the main class “t1”, the line:

t2 x1 = new t2();

creates a new instance of the class “t2”, and named it “x1”.

The line:

double m = x1.square(3);

calls the “square” method of “x1”, and assign the result to “m”.

In java, all numbers have a type. All method definition must declare a type for each of their parameter, and declare a type for the thing the method returns.

Java Doc: Math