Write a java code to print following pattern

1
23
456

Solution:

class printPattern
{
     public static void main(String abc[])
     {
        int counter=1;    
        for(int i=1;i<4;i++)
        {                    
            for(int j=1;j<=i;j++)
              {
                System.out.print(counter);
                counter++;
              }
              System.out.println();
         }
     }
}

Write a java code to print following pattern

A
BB
CCC
DDDD


Solution:

class printABCD
{
     public static void main(String abc[])
     {
        int alphabet=65;                          //ASCII value of A
        for(int i=1;i<5;i++)
        {
            for(int j=1;j<=i;j++)
              {
                System.out.print((char)alphabet);
              }
                System.out.println();
                alphabet++;
         }
     }
}

Is it possible to overload main() method of java. If yes, explain with example.

Ans:
Yes, it is possible to overload main() method in java. You can have more than one main method but with different argument list.
A simple example of overloading main method:

//Test.java
class Test
{
public static void main(String abc[])
{
System.out.println("In Main method");
main(10);
}
static void main(int num)
{
System.out.println("Overloaded main method : prints number :" + num);
}
}

Create multiple threads in java and assign different sleep() time to each Thread.

//Test.java

class simpleThread extends Thread
{
public simpleThread(String str)
{
super(str);
}
public void run()
{
for(int i=0;i<5;i++)
{
try{
String threadName=getName();
if(threadName.equals("A")){
System.out.println(i +": Thread Name: " + getName());
sleep(1000);
}
else if(threadName.equals("B")){
System.out.println("                    "+i +": Thread Name: " + getName());
sleep(3000);
}
else
{
System.out.println("                                        "+i +": Thread Name: "+ getName());
sleep(5000);
}
}
catch(Exception e){System.out.println(e);}
}
}
}

class Test
{
public static void main(String abc[])
{
System.out.println("-----------------------------------------------------------");
new simpleThread("A").start();
new simpleThread("B").start();
new simpleThread("C").start();
}
}

Simple example of Multi Threading in java. Create multiple threads in java.

//Test.java

class simpleThread extends Thread
{
public simpleThread(String str)
{
super(str);
}
public void run()
{
for(int i=0;i<5;i++)
System.out.println(i +": Thread Name: " + getName());
{
try{
sleep(1000);
}
catch(Exception e){System.out.println(e);}
}
}
}

class Test
{
public static void main(String abc[])
{
System.out.println("-----------------------------------------------------------");
new simpleThread("A").start();
new simpleThread("B").start();
}
}

Static Initialization Blocks with a simple example

A static initialization block is a normal block of code enclosed 
in braces, { }, and preceded by the static keyword. Here is an example: 

static { 
 // whatever code is needed for initialization goes here
} 

A class can have any number of static initialization blocks, and they can appear anywhere in the class body. 
The run-time system guarantees that static initialization blocks are called in the order that they appear in the source code.
For example,
Consider following code.

class StaticBlockDemo 
{ 
static 
{ 
System.out.println("I am in static block 1"); 
} 
static 
{ 
System.out.println("I am in static block 2"); 
} 
public static void main(String args[]) 
{ 
System.out.println("I am in main() method"); 
} 
}

Output:
 
I am in static block 1
I am in static block 2
I am in main() method

So you can see that static block initialization takes place before main() method. 
Static blocks are executed sequentially. Here we have two static blocks. 
Block 1 executed prior to Block 2. 
If we change order of blocks to something like 

static 
{ 
System.out.println("I am in static block 2"); 
} 

static 
{ 
System.out.println("I am in static block 1"); 
} 

 
then output will be

I am in static block 2
I am in static block 1

 
Use of static block:

Generally, static block is used to perform initialization.

Write a java code to print goat

class goat
{
public static void main(String abc[])
{
System.out.println();
System.out.println();
System.out.println("               <___>");
System.out.println("               (o-o) ");
System.out.println("   +============\\_/  ");
System.out.println("  / || %%%%%  ||      ");
System.out.println(" /  || %%%%%  ||      ");
System.out.println("*   ||--------||      ");
System.out.println("    \"\"        \"\"      ");
}
}

Note: Just copy paste the above code in notepad file and run it. I hope you will enjoy this. Also, from this code you will learn about the importance of escape characters in a program.