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4. Methods and Method Overloading in Java

• Java Methods.
• Java Methods.

Create a new Eclipse project named task04. Use a package named ua.khpi.oop.your_first_name.task04 for all created classes.

1) Add a class called One to your package. Give it a method named square that will take an integer and return the square of the integer. For example, if you pass in 3, it should return 9. Your overall code will look roughly like this:

class One {
	public static int square(int x) {
		// Calculate and return the square of 'x'.
		return 0;
	}
}

2) Add a second method named power to your class. Return the result of x raised to yth power. For example, if your main method calls power(2, 3), it should return 8.

public static int power(int x, int y) {
	// Return the result of 'x' raised to 'y'th power.
	return 0;
}

3) Add a third method named power to your class. This one should be similar to your second method, but shouldn’t return any value. Pass an object of class A to this method. Modify the object to save the result.

public static void power(A a, int y) {
	// Raise 'a.x' to the 'y'th power.
}

Pre-create a simple class A:

class A {
	int x;
}

4) Add a fourth method named power to your class. Pass an array to this method. Raise each element of an array to the yth power.

public static void power(int[] array, int y) {
	// Raise each element of an array to the 'y'th power.
}

5) Use the following class Main to test the implemented methods of class One.

class Main {
	public static void main(String[] args) {
		System.out.println("Begin...");
		// Use the following VM arguments: -enableassertions
		{
			int x = 3;
			int y = 2;
			int expected = 9;
			int actual = One.power(x, y);
			// Is the 'expected' equal to the 'actual'?
			assert expected == actual : "expected = " + expected + " but actual = " + actual;
		}
		{
			A actual = new A();
			actual.x = 3;
			int y = 2;
			int expected = 9;
			One.power(actual, y);
			// Is the 'expected' equal to the 'actual.x'?
			assert expected == actual.x : "expected = " + expected + " but actual = " + actual.x;
		}
		{
			int[] actual = { 1, 2, 3, 4, 5 };
			int y = 2;
			int[] expected = { 1, 4, 9, 16, 25 };
			One.power(actual, y);
			// Is the 'expected' equal to the 'actual'?
			assert Arrays.equals(expected, actual) : "expected = " + Arrays.toString(expected) + " but actual = "
					+ Arrays.toString(actual);
		}
		System.out.println("Done.");
	}
}

Note: There are two kinds of types in the Java programming language: primitive types (byte, short, int, long, char, float, double, boolean) and reference types (class, interface, array). There are, correspondingly, two kinds of data values that can be stored in variables, passed as arguments, returned by methods, and operated on: primitive values and reference values.

An object is a dynamically created instance of a class type or a dynamically created array. The values of a reference type are references to objects.

Primitive values do not share state with other primitive values.

Extra

Create a Java program to demonstrate method overloading:

• by changing data type of arguments;
• by changing arguments number.

Help: The Java Tutorials - Defining Methods.

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