Thread: Making Methods

I have to write a program that will define a number of public static methods:



add
takes two doubles, returns their sum
max
takes two doubles, returns the larger value (3.0 is larger than -10.0)
rev
takes a String, returns the reversed String ("Hi, Bob" reversed is "boB ,iH")
pi
takes nothing, returns exactly 3.14159
store
takes a double, remembers it, returns nothing
recall
takes nothing, returns the last double from store
even
takes an int, returns true or false if it’s even or not
iota
takes an int (let’s call it n), returns an array of n ints containing 1001, 2002, 3003, ..., n*1001.
Assume that n > 0.
sum
takes an array of doubles, returns their sum
mean
takes an array of doubles, returns their mean (total divided by how many). It must call the sum method to calculate the total. Assume that the array is non-empty.


I start with this. It seems really easy. But I'm not sure where to go. Can someone help me or do the first few methods so I know how to start? Thanks

package Methods;
 
import java.util.Scanner;
 
public class Methods {
 
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int[] a;
        boolean b;
        int n;
        double d;
        String s;
 
        for (;;) {
            System.out.println("Enter command and arguments");
            String op = scan.next();
            if (op.equals("quit"))
                break;
            else if (op.equals("add")) {
                d = add(scan.nextDouble(), scan.nextDouble());
                System.out.println(d);
            }
            else if (op.equals("max")) {
                d = max(scan.nextDouble(), scan.nextDouble());
                System.out.println(d);
            }
            else if (op.equals("rev")) {
                s = rev(scan.nextLine());
                System.out.println(s);
            }
            else if (op.equals("pi")) {
                d = pi();
                System.out.println(d);
            }
            else if (op.equals("store")) {
                store(scan.nextDouble());
            }
            else if (op.equals("recall")) {
                d = recall();
                System.out.println(d);
            }
            else if (op.equals("even")) {
                b = even(scan.nextInt());
                System.out.println(b);
            }
            else if (op.equals("iota")) {
                a = iota(scan.nextInt());
                for (int i=0; i<a.length; i++)
                        System.out.print(a[i] + " ");
                System.out.println();
            }
            else if (op.equals("sum")) {
                scan.skip(" ");
                s = scan.nextLine();
                int count = s.split(" ").length;
                Scanner linescan = new Scanner(s);
                double[] data = new double[count];
                for (int i=0; i<data.length; i++)
                        data[i] = linescan.nextDouble();
                d = sum(data);
                System.out.println(d);
            }
            else if (op.equals("mean")) {
                scan.skip(" ");
                s = scan.nextLine();
                int count = s.split(" ").length;
                Scanner linescan = new Scanner(s);
                double[] data = new double[count];
                for (int i=0; i<data.length; i++)
                        data[i] = linescan.nextDouble();
                d = mean(data);
                System.out.println(d);
            }
            else {
                System.out.println("Invalid command: " + op);
            }
        }
    }
 
}

This is not a code service. It is your homework not ours. You write the code or at least make an attempt. When you get stuck post your code, error messages and ask a specific question. "It doesn't work" is neither a question nor specific.

Okay i've done some of them. Im not sure how to do the methods:

rev
store
recall
iota
sum
mean

This is what I have so far:

package Methods;
 
import java.util.Scanner;
 
public class Methods {
 
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int[] a;
        boolean b;
        int n;
        double d;
        String s;
 
        for (;;) {
            System.out.println("Enter command and arguments");
            String op = scan.next();
            if (op.equals("quit"))
                break;
            else if (op.equals("add")) {
                d = add(scan.nextDouble(), scan.nextDouble());
                System.out.println(d);
            }
            else if (op.equals("max")) {
                d = max(scan.nextDouble(), scan.nextDouble());
                System.out.println(d);
            }
            else if (op.equals("rev")) {
                s = rev(scan.nextLine());
                System.out.println(s);
            }
            else if (op.equals("pi")) {
                d = pi();
                System.out.println(d);
            }
            else if (op.equals("store")) {
                store(scan.nextDouble());
            }
            else if (op.equals("recall")) {
                d = recall();
                System.out.println(d);
            }
            else if (op.equals("even")) {
                b = even(scan.nextInt());
                System.out.println(b);
            }
            else if (op.equals("iota")) {
                a = iota(scan.nextInt());
                for (int i=0; i<a.length; i++)
                        System.out.print(a[i] + " ");
                System.out.println();
            }
            else if (op.equals("sum")) {
                scan.skip(" ");
                s = scan.nextLine();
                int count = s.split(" ").length;
                Scanner linescan = new Scanner(s);
                double[] data = new double[count];
                for (int i=0; i<data.length; i++)
                        data[i] = linescan.nextDouble();
                d = sum(data);
                System.out.println(d);
            }
            else if (op.equals("mean")) {
                scan.skip(" ");
                s = scan.nextLine();
                int count = s.split(" ").length;
                Scanner linescan = new Scanner(s);
                double[] data = new double[count];
                for (int i=0; i<data.length; i++)
                        data[i] = linescan.nextDouble();
                d = mean(data);
                System.out.println(d);
            }
            else {
                System.out.println("Invalid command: " + op);
            }
        }
    }
 
	private static double recall() {
		// TODO Auto-generated method stub
		return 0;
	}
 
	public static double mean(double[] data) {
		// TODO Auto-generated method stub
		return 0;
	}
 
	public static double sum(double[] data) {
		// TODO Auto-generated method stub
		return 0;
	}
 
	public static int[] iota(int nextInt) {
		int n = nextInt;
		int[] a = new int[n];
		return null;
	}
 
	public static boolean even(int nextInt) {
		if (nextInt % 2 == 0)
			return true;
		else
			return false;
	}
 
	public static double store(double nextDouble) {
		double d = nextDouble;
		return d;
 
	}
 
	public static double add(double nextDouble, double nextDouble2) {
		double d = nextDouble + nextDouble2;
		return d;
	}
 
	public static double max(double nextDouble, double nextDouble2) {
		if (nextDouble > nextDouble2)
			return nextDouble;
		else	
			return nextDouble2;
	}
 
	public static String rev(String nextLine) {
		Scanner scan = new Scanner(System.in);
		String rev = scan.nextLine();
		for(int i=rev.length()-1; i > 0; i--)
			System.out.print(i);
		String s = i;
		return s;
	}
 
	public static double pi() {
 
		return 3.14159;
	}
 
}

rev: I know i have to take a string and loop through each character starting from the end and remembering each character so i can place it in another string which is the reverse, but i am unsure how to do the loop and how to convert it to a string.

store: I think i have correctly stored what i am supposed to, the problem is in the recall.

recall: I cant figure out how to recall the variable stored in the store method, extended the braces from the store method to the recall method wont work so i dont know what else to do.

iota: I am unfamiliar with arrays. I think i correctly took the number and made an array with a

sum: Once i learn more how to work with arrays i can do this part. I just need to remember each number in each part of the array and add it to the next number in the array.

mean: This is the same as the sum method, except divide the answer by the number of objects in the array.


Now can someone help me?

ive tried that, hence why im stuck