Pattern Program in java Part-1

#1 Java Program To print Numbers in Below pattern: 

              1 
             2 3 
            4 5 6 
           7 8 9 10 
         11 12 13 14 15

1. package com.javatutorial;
2. public class NumbersFormat {
3.  
4.  public static void main(String[] args) {
5.  
6.  int num=15;
7.  int temp=1;
8.      
9.  for (int i = 1; i <= num; i++)
10.  {
11.  
12.   for (int k = i; k <num; k++)
13.    System.out.print(" ");
14.    for (int j =1; j <= i; j++){
15.  
16.     System.out.print("" +temp+ " ");
17.      temp++;
18.  
19.  if(temp>15){
20.        break;
21.  }
22.  
23.  }
24.  
25.   System.out.println();
26.  
27. if(temp>15){
28.      break;
29.   }
30.  
31. }
32.  
33. }
34. 
    
35. }

Output:

1.               1 
                2 3 
               4 5 6 
              7 8 9 10 
             11 12 13 14 15

# Java Program to print Numbers in Below Format:

1 
1 2 
1 2 3 
1 2 3 4 
1 2 3 4 5 
1 2 3 4 5 6 
1 2 3 4 5 6 7 
1 2 3 4 5 6 7 8 
1 2 3 4 5 6 7 8 9 
1 2 3 4 5 6 7 8 9 10 

1. package learnJavaOnline;
2. public class NumbersFormat {
3. public static void main(String[] args) {
4.  
5. int r, c;
6.  
7. for (r = 1; r <= 10; r++) {
8.  
9. for (c = 1; c <= r; c++) {
10.  
11. System.out.print(c + " ");
12.  
13. }
14.  
15. System.out.println("");
16. }
17.  
18. }
19.  
20. }

Output:

1. 1 
2. 1 2 
3. 1 2 3 
4. 1 2 3 4 
5. 1 2 3 4 5 
6. 1 2 3 4 5 6 
7. 1 2 3 4 5 6 7 
8. 1 2 3 4 5 6 7 8 
9. 1 2 3 4 5 6 7 8 9 
10. 1 2 3 4 5 6 7 8 9 10

#3 Java Program to print numbers in below format

1 2 3 4 5 6 7 8 9 
1 2 3 4 5 6 7 8 
1 2 3 4 5 6 7 
1 2 3 4 5 6 
1 2 3 4 5 
1 2 3 4 
1 2 3 
1 2 
1 

1. package com.learnJava;
2. public class NumbersFormat {
3. public static void main(String[] args) {
4.  
5. int r, c;
6.  
7. for (r = 1; r <= 10; r++) {
8.  
9. for (c = 1; c <= 10-r; c++) {
10.  
11. System.out.print(c + " ");
12.  
13. }
14.  
15. System.out.println("");
16. }
17.  
18. }
19.  
20. }

Output:

1. 1 2 3 4 5 6 7 8 9 
2. 1 2 3 4 5 6 7 8 
3. 1 2 3 4 5 6 7 
4. 1 2 3 4 5 6 
5. 1 2 3 4 5 
6. 1 2 3 4 
7. 1 2 3 
8. 1 2 
9. 1 

throw keyword in java with example

Throw keyword in java

• Throw keyword is used to throw exception manually.
• Whenever it is required to suspend the execution of the functionality based on the user defined logical error condition we will use this throw keyword to throw exception.
• So we need to handle these exceptions also using try catch blocks.

 Java simple example Program to explain use of throw keyword in java

1. package exceptions;
2.  
3. public class ThrowKeyword {
4.  
5.     
6. public static void main(String[] args) {
8.  
9. try {
10.             
11.    throw new ArithmeticException();
12.             
13.             
14. } catch (Exception e) {
15.  
16.    System.out.println(e);
17.    e.printStackTrace();
18. }
19.  
20. }
21.  
22. }

Output:

1. java.lang.ArithmeticException
2. java.lang.ArithmeticException
3.     at exceptions.ThrowKeyword.main(ThrowKeyword.java:11)

Rules to use "throw" keyword in java 

• throw keyword must follow Throwable type of object.
• It must be used only in method logic.
• Since it is a transfer statement , we can not place statements after throw statement. It leads to compile time error Unreachable code

•  We can throw user defined exception using throw keyword.

1. //Custom exception
2. package com.instanceofjavaforus;
3. public class InvalidAgeException extends Exception {
4.  InvaidAgeException(String msg){
5.  super(msg);
6.  }
7. }
    

1. package com.exceptions;
2. public class ThrowDemo {
3. 
   
4. public boolean isValidForVote(int age){
5.  
6.  try{
7.    if(age<18){
8.   throw new InvalidAgeException ("Invalid age for voting");
9. }
10.  }catch(Exception e){
11.  System.out.println(e);
12.  }
13.   return false;
14.  }
15.  
16. public static void main(String agrs[]){
17.  
18.  ThrowDemo obj= new ThrowDemo();
19.    obj.isValidForVote(17);
20.  
21.   }
22. }

 Output:

1.  exceptions.InvalidAgeException: Invalid age for voting

• We can throw predefined exceptions using throw keyword

1. package com.instanceofjava;
2.  
3. public class ThrowKeyword{
4. public void method(){
5.  
6.  try{
7.   
8.   throw new NullPointerException("Invalid age for voting");
9. }
10.  }catch(Exception e){
11.  System.out.println(e);
12.  }
13.  }
14.  
15.   public static void main(String agrs[]){
16.  
17.  ThrowKeyword obj= new ThrowKeyword();
18.  
19.    obj.method();
20.  
21.   }
22. }

 Output:

1.  java.lang.NullPointerException: Invalid age for voting