The operator <= is undefined for the argument type int, Distance and more errors

I think I got the codes right on the Distance.java. Just stuck at trying to show the loop output from the Driver.java.

The problem is that it says "the operator <= is undefined for the argument type int, Distance" and "hours" is a duplicate local variable.

"The operator <= is undefined for the argument type int, Distance" is probably due to the fact that "distance.getDistance(distance);" being shown as a string. but how would I make it a double? And how would I solve the "hours" problem.

public class Distance {

	// creating private statement
	private double speed;
	private int hours;

	// creating a Distance method
	public Distance() {

		// creating getters and setters
	}

	public double getSpeed() {
		return speed;
	}

	public void setSpeed(double speed) {
		this.speed = speed;
	}

	public int getHours() {
		return hours;
	}

	public void setHours(int hours) {
		this.hours = hours;
	}

	// setting up distance equation
	public double getDistance(double distance) {
		return distance = hours * speed;
	}
}

import java.util.Scanner;

public class Driver {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		// setting up a scanner
		Scanner scanner = new Scanner(System.in);

		// creating objects
		Distance speed = new Distance();
		Distance hours = new Distance();
		Distance distance = new Distance();

		distance.getDistance(distance);

		// input for vehicle speed and hour
		System.out.println("Please enter vehicle speed: ");
		scanner.nextDouble();
		speed.setSpeed(scanner.nextDouble());

		System.out.println("Please enther hours vehicle was in motion: ");
		scanner.nextInt();
		hours.setHours(scanner.nextInt());

		System.out.println("Hour\tDistance Travelled\n----\t----------");
		for (int hours = 1; hours <= distance; hours++) {

		}
	}
}

Well, you defined two variables with the name hours:

• here: Distance hours = new Distance();
• and here: for (int hours = 1; hours <= distancel; hours++)

And about the <=: you are trying to compare complex objects, since hours (the first definition) and distance are instances of Distance class. Therefore, the two errors.

The operator <= is meant to be used with the primitive types (e.g. int, long, double etc.) or their boxed types (e.g. Integer, Long, Double etc.), not for other types.

You do not need to create as many objects as for each input as long as the inputs are supposed to be for just one object. Also, the getDistance function needs to be changed to return the distance based on speed and time without requiring the distance to be passed to it as a parameter.

import java.util.Scanner;

class Distance {
	private double speed;
	private int hours;

	public double getSpeed() {
		return speed;
	}

	public void setSpeed(double speed) {
		this.speed = speed;
	}

	public int getHours() {
		return hours;
	}

	public void setHours(int hours) {
		this.hours = hours;
	}

	public double getDistance() {
		return hours * speed;
	}
}

public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);

		// Creating an object of Distance
		Distance distance = new Distance();

		// Input for vehicle speed and hour
		System.out.print("Please enter vehicle speed: ");
		distance.setSpeed(scanner.nextDouble());

		System.out.print("Please enter hours vehicle was in motion: ");
		distance.setHours(scanner.nextInt());

		// Display the result
		System.out.printf("Hour: %d, Speed: %f, Distance Travelled: %f", distance.getHours(), distance.getSpeed(),
				distance.getDistance());
	}
}

A sample run:

Please enter vehicle speed: 50.5
Please enter hours vehicle was in motion: 5
Hour: 5, Speed: 50.500000, Distance Travelled: 252.500000

Have a look at JLS §15.20.1:
>The type of each of the operands of a numerical comparison operator must be a type that is convertible (§5.1.8) to a primitive numeric type, or a compile-time error occurs.

Your distance is a reference type variable, that cannot be an operand used with a <= numerical operator. Both of this operator's operands must be primitives, or anything that can be unboxed to the primitives.