Commandline Arguments in Java

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What is the commandline arguments mean in java?

command line arguments are parameters that are supplied to the application program at the time of starting its execution. They must be supplied at the time of its execution after the filename.

we can pass any number of commandline arguments while launching an application

Normally we execute the program by using below commands

• javac filename.java
• java filename

How to pass commandline arguments?

• javac filename.java
• java filename argument1 < space > argument2 < space >... argumentN

Everything you pass from commandline argument is considered as inString format.

Lets see below program to understand best use of commandline argument

Example

Qn. Develop a program to print string using commandline argument

class First
{
   public static void main(String args[])
   {
     System.out.println("You have passed : "+args[0]);
   }
}

Compile above program by using following steps

• javac filename.java
• java classname AndroidBerry.com

Output

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How to pass multiple arguments?

By default the arguments are considered as String. We have need to convert them into the respective datatype by using type casting.

If you want to store integer value into variable we use int a = Integer.parseInt(arg[0]);

Example

Develop a program to find addition of two numbers using commandline argument.

class Addition
{
    public static void main(String args[])
    {
	int a = Integer.parseInt(args[0]);
	int b = Integer.parseInt(args[1]);

	System.out.println("A : "+args[0]);
	System.out.println("B : "+args[1]);

	System.out.println("Addition = "+ a+b);
    }
}

Compile the program using

• Step1 - javac Addition.java
• Step2 - java Addition 10 20

Output

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How does multiple argument work?

• In public static void main(String args[]) : the args is an object of type string which contain empty brackets as [ ]. this means that args[] able to get any number string arguments because we have not specified any size like args[10] etc.
• The very first value is received into the args[0] index and second value is in args[1]. thats why we have specified the indexes of each value while converting into integer.
• Integer is an object which contains the method (function) called parseInt() : which is used for conversion of string into integer type

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How to convert String into other types?

java allows us to convert the string into following datatypes

1. Integer - Integer.parseInt(value);
2. Float - Float.parseFloat(value);
3. Double - Double.parseDouble(value)

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