Programs to print triangles using *, numbers and characters
Program to print half pyramid using *

*
* *
* * *
* * * *
* * * * *

Source code
public class Pattern {
public static void main(String[] args) {
int rows = 5;

for(int i = 1; i <= rows; ++i) {
for(int j = 1; j <= i; ++j) {
System.out.print("* ");
}
System.out.println();
}
}
}

Program to print half pyramid a using numbers
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5;

for(int i = 1; i <= rows; ++i) {
for(int j = 1; j <= i; ++j) {
System.out.print(j + " ");
}
System.out.println();
}
}
}

Program to print half pyramid using alphabets
A
B B
C C C
D D D D
E E E E E

Source Code
public class Pattern {

public static void main(String[] args) {
char last = 'E', alphabet = 'A';

for(int i = 1; i <= (last-'A'+1); ++i) {
for(int j = 1; j <= i; ++j) {
System.out.print(alphabet + " ");
}
++alphabet;

System.out.println();
}
}
}

Programs to print inverted half pyramid using * and numbers
Inverted half pyramid using *

* * * * *
* * * *
* * *
* *
*

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5;

for(int i = rows; i >= 1; --i) {
for(int j = 1; j <= i; ++j) {
System.out.print("* ");
}
System.out.println();
}
}
}

Java Program to Check Leap Year

Inverted half pyramid using numbers
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5;

for(int i = rows; i >= 1; --i) {
for(int j = 1; j <= i; ++j) {
System.out.print(j + " ");
}
System.out.println();
}
}
}

Programs to display pyramid and inverted pyramid using * and digits
Program to print full pyramid using *

*
* * *
* * * * *
* * * * * * *
* * * * * * * * *

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5, k = 0;

for(int i = 1; i <= rows; ++i, k = 0) {
for(int space = 1; space <= rows - i; ++space) {
System.out.print("  ");
}

while(k != 2 * i - 1) {
System.out.print("* ");
++k;
}

System.out.println();
}
}
}

Program to print pyramid using numbers
1
2 3 2
3 4 5 4 3
4 5 6 7 6 5 4
5 6 7 8 9 8 7 6 5

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5, k = 0, count = 0, count1 = 0;

for(int i = 1; i <= rows; ++i) {
for(int space = 1; space <= rows - i; ++space) {
System.out.print("  ");
++count;
}

while(k != 2 * i - 1) {
if (count <= rows - 1) {
System.out.print((i + k) + " ");
++count;
}
else {
++count1;
System.out.print((i + k - 2 * count1) + " ");
}

++k;
}
count1 = count = k = 0;

System.out.println();
}
}
}

Java Program to Check Whether a Character is Alphabet or Not

Inverted full pyramid using *
* * * * * * * * *
* * * * * * *
* * * * *
* * *
*

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 5;

for(int i = rows; i >= 1; --i) {
for(int space = 1; space <= rows - i; ++space) {
System.out.print("  ");
}

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

for(int j = 0; j < i - 1; ++j) {
System.out.print("* ");
}

System.out.println();
}
}
}

Print Pascal's triangle
1
1   1
1   2   1
1   3   3    1
1   4   6   4   1
1   5   10   10  5   1

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 6, coef = 1;

for(int i = 0; i < rows; i++) {
for(int space = 1; space < rows - i; ++space) {
System.out.print("  ");
}

for(int j = 0; j <= i; j++) {
if (j == 0 || i == 0)
coef = 1;
else
coef = coef * (i - j + 1) / j;

System.out.printf("%4d", coef);
}

System.out.println();
}
}
}

Print Floyd's Triangle.
1
2 3
4 5 6
7 8 9 10

Source Code
public class Pattern {

public static void main(String[] args) {
int rows = 4, number = 1;

for(int i = 1; i <= rows; i++) {

for(int j = 1; j <= i; j++) {
System.out.print(number + " ");
++number;
}

System.out.println();
}
}
}

Java Program to Check Whether a Number is Palindrome or Not