1. Show Main Thread

1. Write a program to display the name of thread while executing the main() method.
Solution

class ShowMyName{
      public static void main(String[] args){
             String threadName = Thread.currentThread().getName();
             System.out.println("The name of current thread is "+threadName);
      }
}

after compilation, run the program and see the result as follows:
prompt>java ShowMyName
The name of current thread is main

Hello Name - 2

3. Write a program in java to print "Hello Name" using command line argument with taking care of possible runtime exception.
Solution

class User{
     public static void main(String[]  args){
         String name = "";
         if(args.length==1)name = args[0];
         System.out.println("Hello "+name);
     }
}

After compilation, run this program as follows and watch the output in next line:
prompt>java User Amit
Hello Amit

prompt>java User
Hello

Hello Name

2. Write a program in java to print "Hello Name" where Name will be passed as command line argument at run time.
Solution:

class User{
     public static void main(String[]  args){
         String name = args[0];
         System.out.println("Hello "+name);
     }
}

After compilation, run this program as follows and watch the output in next line:
prompt>java User Amit
Hello Amit

Caution: if nothing is passed from command line argument, it will show an Run-time Exception as ArrayIndexOutOfBoundsException, as there will be no element in the String array 'args'.

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Excercise Solution 1

1. Write a program in java to print or display "Hello World".
class User{
       public static void main(String[] args){
              System.out.println("Hello World");
      }
}

Save the above code into a file, let us say User.java
Compile the source file from the command prompt:
prompt>javac User.java
Now you will have two files, one is your source file User.java and another one is the compiled file namely User.class
Now execute your newly born class as follows and watch the output on next line.
prompt>java User
Hello World

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