Java Command Line Arguments

In this tutorial, we will learn about Java command line arguments with the help of examples.

In JavaCommand Line ArgumentsAllowing us to pass parameters during program execution.

As the name suggests, parameters are passed via the command line.

Example: Command Line Arguments

class Main {
　　public static void main(String[] args) {
　　　　System.out.println("Command line arguments are");
　　　　//Traverse all arguments
　　　　for(String str: args) {
　　　　　　System.out.println(str);
　　　　}
　　}
}

Let's try to run the program using the command line.

1.Compile the code

javac Main.java

2.Run the code

java Main

Now, suppose we want to pass some arguments when running the program. We can pass arguments after the class name. For example,

java Main apple ball cat

Here, apple, ball, and cat are the arguments passed to the program via the command line. Now, we will get the following output.

Command Line Arguments are
Apple
Ball
Cat

In the above program, the main() method includes a string array named args as a parameter.

public static void main(String[] args) {...}

A String array stores all the arguments passed via the command line.

NoteParameters are always stored as strings and always enclosed bySpaceSeparated by

Passing Numeric Command Line Arguments

Each Java program's main() method only accepts string arguments. Therefore, it is impossible to pass numeric arguments via the command line.

However, later we can convert string arguments to numeric values.

Example: Numeric Command Line Arguments

class Main {
　　public static void main(String[] args) {
　　　　for(String str: args) {
　　　　　　//Convert to integer type
　　　　int argument = Integer.parseInt(str);
　　　　System.out.println("Integer argument: "　+　argument);
　　　　}
　　}
}

Let's try to run the program through the command line.

//Compile the code
javac Main.java
//Run the code
java Main　11　23

here11and23are command line arguments. Now, we will get the following output.

Arguments in integer form
11
23

In the above example, please note the following line

int argument = Integer.parseInt(str);

Here, the parseInt() method of the Integer class converts the string argument to an integer.

Similarly, we can use the parseDouble() and parseFloat() methods to convert strings to double and float, respectively.

NoteA NumberFormatException is thrown if the argument cannot be converted to the specified numeric value.