How can I draw a Diamond?

Question

import java.util.Scanner;

public class Main 
{
    public static void main(String[] args){
        Scanner input = new Scanner(System.in);
        int x = 0; // input height
        
        int choice;
        
        System.out.println("1. Trapezoid ");
        System.out.println("2. Diamaond ");
        System.out.println("3. Hollow Triangle ");
        System.out.println("What kind of shape do you want to see? ");
        choice = input.nextInt(); // user chooses shape
        
        if(choice==1){
            System.out.print("Enter height: ");
            x = input.nextInt(); //user inputs height
            
            drawTrapezoid(x);
        } else if(choice == 2){
            System.out.print("Enter height: ");
            x = input.nextInt(); //user inputs height
            drawDiamond(x);
        } else if(choice == 3){
            System.out.print("Enter height: ");
            x = input.nextInt(); //user inputs height
            //drawHollowTriangle(x,mark);
        }
        
    }
    

    //Diamond
    public static void drawbDiamond(int length){
        for(int j = 1; j<=length; j++){
            System.out.print('x');
            
        }
    }
    public static void drawbDiamond(int length, char mark){
        for(int j = 1; j<=length; j++){
            System.out.print(mark);
            
        }
    }
    public static void drawbDiamondln(int length){
        drawbDiamond(length);
        System.out.println();
    }
    public static void drawbDiamondln(int length, char mark){
        drawbDiamond(length,mark);
        System.out.println();
    }
    public static void drawDiamond(int x){
        int dotspace = x - 1;
        int xstars = 1;
        do{ //first half of diamond
            drawbDiamond(dotspace,'.');
            drawbDiamondln(xstars);
            dotspace--;
            xstars+=2;
        } while(dotspace>=0);
       
        do{ 
            drawbDiamond(dotspace, '.');
            drawbDiamondln(xstars);
            dotspace++;
            xstars-=2;
        } while(dotspace<=x);
        
    }

    
    
    // TRAPEZOID
    public static void drawbTrapezoid(int length){
        for(int i = 1; i<=length; i++){ 
            System.out.print('x');
        }
        
    }
    public static void drawbTrapezoid(int length, char mark){
        for(int i = 1; i<=length; i++){ 
            System.out.print(mark);
        }
    }
    public static void drawbTrapezoidln(int length){
        drawbTrapezoid(length);
        System.out.println();
    }
    public static void drawbTrapezoidln(int length, char mark){
        for(int i = 1; i<=length; i++){ 
            drawbTrapezoid(length,mark);
        }
    }
    public static void drawTrapezoid(int x){
        
        int dotspace = x - 1;
        int xstars = 2 * x - 1;
        do{
           drawbTrapezoid(dotspace, '.');
           drawbTrapezoidln(xstars);
           dotspace--;
           xstars+=2;
        } while(dotspace>=0);
    }
    
}

Answer 1

Here is my solution.

The idea is that there are 2 different diamonds: one with the height being even and one with odd. The odd is the "classic one" with pointy edges. The even comes with blunt edges for symmetry.

import java.util.Scanner;

public class Main 
{
    private static final char empty = ' ';
    private static final char mark = '*';
    
    private static boolean validate(int number, int min, int max)
    {
        if (number < min || number > max)
        {
            System.out.println("Invalid value entered. It must be between " + min + " and " + max);
            return false;
        }
        
        return true;
    }

    private static void drawTrapezoid(int height)
    {
        int baseWidth = 50;
        while (--height >= 0)
        {
            for (int i = 0; i < height; i++)
                System.out.print(empty);

            int width = baseWidth - height * 2;
            for (int i = 0; i < width; i++)
                System.out.print(mark);

            System.out.println();
        }
    }
    
    private static void drawDiamondSlice(int halfHeight, int halfSliceIndex, int parityMinusOne)
    {
        int emptyWidth = halfHeight - halfSliceIndex + parityMinusOne;
        for (int j = 0; j < emptyWidth; j++)
            System.out.print(empty);
        
        int width = 1 + halfSliceIndex * 2 - parityMinusOne;
        for (int j = 0; j < width; j++)
            System.out.print(mark);

        System.out.println();
    }
    
    private static void drawDiamond(int height)
    {
        int parityMinusOne = height % 2 - 1;
        int halfHeight = height / 2;

        // Upper half
        for (int i = 0; i < halfHeight; i++)
            drawDiamondSlice(halfHeight, i, parityMinusOne);

        // Lower half
        for (int i = halfHeight + parityMinusOne; i >= 0; i--)
            drawDiamondSlice(halfHeight, i, parityMinusOne);
    }

    private static void drawHollowTriangle(int height)
    {
        // The tip
        for (int i = 1; i < height; i++)
            System.out.print(empty);

        System.out.println(mark);
        
        // Slices
        for (int i = 2; i < height; i++)
        {
            for (int j = 0; j < height - i; j++)
                System.out.print(empty);
                
            System.out.print(mark);
                
            for (int j = 0; j < (i - 1) * 2 - 1; j++)
                System.out.print(empty);

            System.out.println(mark);
        }
        
        // The base
        if (height > 1)
        {
            int baseWidth = height * 2 - 1;
            for (int i = 0; i < baseWidth; i++)
                System.out.print(mark);
            
            System.out.println();
        }
    }
    
    public static void main(String[] args)
    {
        System.out.println("1. Trapezoid");
        System.out.println("2. Diamaond");
        System.out.println("3. Hollow Triangle");
        System.out.println("What kind of shape do you want to see? ");

        Scanner input = new Scanner(System.in);
        int choice = input.nextInt();   // User chooses shape
        
        if (!validate(choice, 1, 3))
        {
            System.out.println("Exiting...");
            return;
        }
        
        System.out.print("Enter the height: ");
        int height = input.nextInt();
        if (!validate(height, 1, 20))
        {
            System.out.println("Exiting...");
            return;
        }
        
        switch (choice)
        {
            case 1: drawTrapezoid(height); break;
            case 2: drawDiamond(height); break;
            case 3: drawHollowTriangle(height); break;
            default: return;    // We have actually already handled this above when we validate the choice.
        }
    }
}