Printing *s as triangles in Java?

Question

My assignment in my Java course is to make 3 triangles. One left aligned, one right aligned, and one centered. I have to make a menu for what type of triangle and then input

Answer 1

public static void main(String[] args) {

    System.out.print("Enter the number: ");
    Scanner userInput = new Scanner(System.in);
    int myNum = userInput.nextInt();
    userInput.close();

    System.out.println("Centered Triange");
    for (int i = 1; i <= myNum; i+=1) {//This tells how many lines to print (height)

        for (int k = 0; k < (myNum-i); k+=1) {//Prints spaces before the '*'
            System.out.print(" ");
        }

        for (int j = 0; j < i; j++) { //Prints a " " followed by '*'.   
            System.out.print(" *");
        }

        System.out.println(""); //Next Line     
    }

    System.out.println("Left Triange");
    for (int i = 1; i <= myNum; i+=1) {//This tells how many lines to print (height)

        for (int j = 0; j < i; j++) { //Prints the '*' first in each line then spaces.  
            System.out.print("* ");
        }

        System.out.println(""); //Next Line         
    }

    System.out.println("Right Triange");
    for (int i = 1; i <= myNum; i+=1) {//This tells how many lines to print (height)

        for (int k = 0; k < (myNum-i); k+=1) {//Prints spaces before the '*'
            System.out.print("  ");
        }

        for (int j = 0; j < i; j+=1) { //Prints the " " first in each line then a "*".  
            System.out.print(" *");
        }

        System.out.println(""); //Next Line         
    }

}

Answer 2

This is the least complex program, which takes only 1 for loop to print the triangle. This works only for the center triangle, but small tweaking would make it work for other's as well -

import java.io.DataInputStream;

public class Triangle {
    public static void main(String a[]) throws Exception{
        DataInputStream in = new DataInputStream(System.in);

        int n = Integer.parseInt(in.readLine());
        String b = new String(new char[n]).replaceAll("\0", " ");
        String s = "*";
        for(int i=1; i<=n; i++){
            System.out.print(b);
            System.out.println(s);
            s += "**";
            b = b.substring(0, n-i);
            System.out.println();
        }
    }
}

Answer 3

For the right triangle, for each row :

• First: You need to print spaces from 0 to rowNumber - 1 - i.
• Second: You need to print \* from rowNumber - 1 - i to rowNumber.

Note: i is the row index from 0 to rowNumber and rowNumber is number of rows.

For the centre triangle: it looks like "right triangle" plus adding \* according to the row index (for ex : in first row you will add nothing because the index is 0 , in the second row you will add one ' * ', and so on).

Answer 4

package apple;

public class Triangle
{
private static final int row = 3;

public static void main(String...strings){
    printLeftTrangle();
    System.out.println();
    printRightTrangle();
    System.out.println();
    printTrangle();
}

/*  Pattern will be
     *
     **
     ***
     ****
 */

public static void printLeftTrangle(){

    for(int y=1;y<=row;y++){
     for(int x=1;x<=y;x++)
         System.out.print("*");
     System.out.println();
    }
}

/*  Pattern will be
        *
       **
      ***
     ****
 */
public static void printRightTrangle(){
    for(int y=1;y<=row;y++){
        for(int space=row;space>y;space--)
            System.out.print(" ");
        for(int x=1;x<=y;x++)
            System.out.print("*");
        System.out.println();
    }
}

/*  Pattern will be
     *
    ***
   *****
*/

public static void printTrangle(){

    for(int y=1, star=1;y<=row;y++,star +=2){
        for(int space=row;space>y;space--)
            System.out.print(" ");
        for(int x=1;x<=star;x++)
            System.out.print("*");
        System.out.println();
    }
}
}

Answer 5

import java.util.Scanner;

public class A {

    public void triagle_center(int max){//max means maximum star having
        int n=max/2;
        for(int m=0;m<((2*n)-1);m++){//for upper star
            System.out.print(" ");
        }
        System.out.println("*");

        for(int j=1;j<=n;j++){
            for(int i=1;i<=n-j; i++){
                System.out.print("  ");
            }
            for(int k=1;k<=2*j;k++){
            System.out.print("* ");
            }

            System.out.println();
        }


    }

    public void triagle_right(int max){
        for(int j=1;j<=max;j++){
            for(int i=1;i<=j; i++){
                System.out.print("* ");
            }

            System.out.println();
        }
    }

    public void triagle_left(int max){
        for(int j=1;j<=max;j++){
            for(int i=1;i<=max-j; i++){
                System.out.print("  ");
            }
            for(int k=1;k<=j; k++){
                System.out.print("* ");
            }

            System.out.println();
        }
    }

    public static void main(String args[]){
        A a=new A();
        Scanner input = new Scanner (System.in);
        System.out.println("Types of Triangles");
        System.out.println("\t1. Left");
        System.out.println("\t2. Right");
        System.out.println("\t3. Center");
        System.out.print("Enter a number: ");
        int menu = input.nextInt();
        Scanner input1 = new Scanner (System.in);
        System.out.print("maximum Stars in last row: ");
        int row = input1.nextInt();
        if (menu == 1)
            a.triagle_left(row);
        if (menu == 2)
            a.triagle_right(row);
        if (menu == 3)
            a.triagle_center(row);
    }
}

Answer 6

Left alinged triangle- * **

---

---

from above pattern we come to know that-
1)we need to print pattern containing n rows (for above pattern n is 4).
2)each  row contains star and no of stars i each row is incremented by 1.
So for Left alinged triangle we need to use 2 for loop.
1st "for loop" for printing n row.
2nd  "for loop for printing stars in each rows. 


 Code for  Left alinged triangle-

 public static void leftTriangle()
{
       /// here  no of rows is 4
 for (int a=1;a<=4;a++)// for loop for row
 {   
 for (int b=1;b<=a;b++)for loop for column
 {
 System.out.print("*");
 }

System.out.println();}
}

---

Right alinged triangle- *
**

---

---

from above pattern we come to know that-
1)we need to print pattern containing n rows (for above pattern n is 4).
 2)In each  row we need to print spaces followed by a star & no of spaces            in each row is decremented by 1.
 So for Right alinged triangle we need to use 3 for loop.
 1st "for loop" for printing n row.
 2nd  "for loop for printing spaces.
 3rd "for loop" for printing stars.

Code for Right alinged triangle -

public void rightTriangle()
{
    // here 1st print space and then print star
  for (int a=1;a<=4;a++)// for loop for row
 { 
 for (int c =3;c>=a;c--)// for loop fr space
 {  
 System.out.print(" ");
 }
 for (int d=1;d<=a;d++)// for loop for column
 { 
 System.out.print("*");   
 }
 System.out.println(); 
 }
 }

---

Center Triangle- *
* *

---

---

from above pattern we come to know that- 1)we need to print pattern containing n rows (for above pattern n is 4). 2)Intially in each row we need to print spaces followed by a star & then again a space . NO of spaces in each row at start is decremented by 1. So for Right alinged triangle we need to use 3 for loop. 1st "for loop" for printing n row. 2nd "for loop for printing spaces. 3rd "for loop" for printing stars.

Code for center Triangle-

public  void centerTriangle()
{   
for (int a=1;a<=4;a++)// for lop for row
{   
for (int c =4;c>=a;c--)// for loop for space
{  
System.out.print(" ");
}
for (int b=1;b<=a;b++)// for loop for column
{
System.out.print("*"+" ");
}
System.out.println();}
}

---

CODE FOR PRINTING ALL 3 PATTERNS - public class space4 { public static void leftTriangle() { /// here no of rows is 4 for (int a=1;a<=4;a++)// for loop for row {
for (int b=1;b<=a;b++)for loop for column { System.out.print("*"); }

System.out.println();}
}

public static void rightTriangle()
{
    // here 1st print space and then print star
  for (int a=1;a<=4;a++)// for loop for row
 { 
 for (int c =3;c>=a;c--)// for loop for space
 {  
 System.out.print(" ");
 }
 for (int d=1;d<=a;d++)// for loop for column
 { 
 System.out.print("*");   
 }
 System.out.println(); 
 }
 }

public static void centerTriangle()
{   
for (int a=1;a<=4;a++)// for lop for row
{   
for (int c =4;c>=a;c--)// for loop for space
{  
System.out.print(" ");
}
for (int b=1;b<=a;b++)// for loop for column
{
System.out.print("*"+" ");
}
System.out.println();}
}
public static void main (String args [])
{
space4 s=new space4();
s.leftTriangle();
s.rightTriangle();
s.centerTriangle();
}
}