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Usage of command-line arguments

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Objective

On completion of this period, you would be able to know,

• The usage of command-line arguments

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Recap

• In the last class we discussed• The String class• Constructors of String class• Methods of String class

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• How to pass information into a program when you run it?

• This is accomplished by passing command-line arguments to main()

• A command line argument is the information that directly follows the programs name on the command-line when it is executed

Usage of command-line arguments

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• To access command-line arguments inside a java program is quite easy

• They are stored as Strings in the String array passed to main()

• For example, the following program displays all of the command-line arguments that it is called with

Usage of command-line arguments contd..

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Example Program : command-line argumentsclass CommandLine {

public static void main (String args[]) {

for(int i=0; i<args.length; i++) {

System.out. println(“ args [ ”+ i “ ] : ”+args[i]);

} // end of for

} // end of main

}// end of class http://improvejava.blogspot.in 6

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Example Program : Command-line Arguments contd..

• Try executing the program as shown here

• Java CommandLine this is a test 100 -1

•When you do, you will see the following output:

Output :args[0] : thisargs[1] : isargs[2] : aargs[3] : testargs[4] : 100args[5] : -1

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• All command-line arguments are passed as strings

• You must convert it into desired format, using wrapper classes

Usage of command-line arguments

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• Usage of command-line arguments that needs conversion

Example Program

class CommandLine {

public static void main (String args[]) {

int a = Integer.parseInt(args[0]);

int b = Integer.parseInt(args[1]);

int c = a + b;

System .out. println(“ sum of the ”+ a + “ and ” + b+ “ is :”+ c);

} // end of main

}// end of class

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Example Program contd..

• Try executing the program as shown here,

• Java CommandLine 10 20

• When you do, you will see the following output

Output : sum of the 10 and 20 is : 30

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• What are the differences between command line arguments in C and Java ?

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Discussion

C Java

Number of arguments

One less than the actual number

Equal to actual number

Type of arguments

Character array String

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• About command line arguments• Usage of command line arguments

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Summary

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1. Command-line arguments are passed from

a. calling method

b. command prompt

c. from JVM

d. from operating system

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Quiz

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Quiz contd..

2. Command-line arguments are stored in

a. Variables

b. Actual parameters

c. int parameter

d. String array

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1. Explain the use of Command-line arguments with an example program?

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Frequently Asked Questions

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1. Write a program in Java that takes command-line arguments and display how many number of parameters passed

2. Write a program in Java that takes command line arguments and that searches for a give is present in command-line arguments

3. Write a program in Java that takes command line arguments and print the parameter in String array in reverse order

Assignment

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