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Ravi Dhoriya ツ
Ravi Dhoriya ツ

Reputation: 4414

Why only String[] args in java instead of Object[] args?

In java, as per the Java Language Specification 12.1.4 the main method should be declared as follows:

public static void main(String[] args){
     //code of program
}

With the use of String[] args we can get command-line arguments. Sometime those command-line arguments needs to be converted to appropriate type. suppose if you have supplied any number 123 as an argument and you want to convert it to int then we can use one of the following conversion methods:

int n1=Integer.valueOf(args[0]);
//or
int n2=Integer.parseInt(args[0]);

But, if java could have provided use of Objects[] args instead String[] args then we can easily convert from one type to another, for this example conversion would take place as follows:

public static void main(Object[] args){
     int n1=(Integer)args[0];
}

I'm not getting this why java have used String[] args and not Object[] args?

Upvotes: 2

Views: 2748

Answers (7)

Jorge Campos
Jorge Campos

Reputation: 23361

This is simple because the args came from outside java environment, it is from the Operating System and as such it can't create Java Objects it can only pass Strings

To call a java program from a console it would be something like:

c:\java MyProgram 123

There is no way to java know that the OS is passing an object it is just a string.

Upvotes: 3

Kishore
Kishore

Reputation: 300

May be because "String" is an array of char sequence which takes continuous memory, and which can be entered using standard keyboard. Otherwise how main method will handle type casting.

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726579

Java is designed with portability in mind, so that Java programs would be invoked by diverse operating environments. Having the environments pass Java objects to main would put too much restrictions on the caller system, because that system would have a task of "understanding" the input and converting it to Java objects.

Strings, on the other hand, are universal: all operating environments have them. Therefore, Java specification required strings, knowing that your Java program would be able to process and understand them better than an external environment.

Upvotes: 7

Elliott Frisch
Elliott Frisch

Reputation: 201447

Because the operating system doesn't pass variable typed arguments to the JVM. If you had Object[] args the JVM couldn't really infer their types like that without the Operating System. It's also the general contract (in Java of course) of "standard" (e.g. ancestral C/C++) Main function.

Upvotes: 1

HJW
HJW

Reputation: 23443

public static void main(String[] args) is a main method that runs when you execute the Class file $java MyClass input1 input2.

Upvotes: 1

Steve P.
Steve P.

Reputation: 14699

Because you cannot pass an object via a command line argument. Instead, it's natural to interpret the passed arguments as Strings.

Upvotes: 1

Sudhakar Tillapudi
Sudhakar Tillapudi

Reputation: 26209

whenever you read from Console it is by default String that is the reason they have made it as String[] array .

if you use :

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter String");
String str = br.readLine();

String variable str by contains String because br.ReadLine() gives you string

Upvotes: 2

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