Java main string arguments

Is there a difference between main(String args[]) and main(String[] args)?

Semantically, they are identical. However, I’d recommend using the latter syntax ( String[] args ) when declaring arrays. The former syntax is there mainly for compatibility with C syntax.

Since String[] , as a whole, is the type of the object in Java, it’s more consistent and clear not to split it up.

A similar question addresses the [] after method argument list.

There’s no difference, but putting the brackets after the type ( String[] ) is the more common practice in Java.

Both of them are absolutely the same. Please refer to Java Language Specification (JLS) to see the syntax used in java.

String[] args or String args[] will create an array (reserves a place in memory) with no size and name args .

Putting the [] after the name avoids subtle problems like this:-

String x [] , y; //x[] is an array but y is a String String [] x y ; //two arrays x[] and y[] both 

Although both are used to create array of String type but second one is more popular, because with that, you can create multiple String arrays simultaneously. E.g String[] a,b; Here you have created two String Arrays a and b simultaneously.

String a[],b; will create String array «a» and String variable(not array) b.

They are just two style of writting

The method signature is the same so there is no difference.

Its a public method, it returns nothing, the method name is «main» and the it takes a String array.

Nope. There is no difference b/w the two.

See Declaring a Variable to Refer to an Array section in this doc. From that doc

float anArrayOfFloats[]; // this form is discouraged

so just use the second style.

The difference between these is that when we try to call the main method manually from one class to another by using static syntax , we use «string[] s «. At that point we have to pass an array of string type as argument in main method. When we are using «String. s» then there is no need to pass any string array as an argument. It will run and it doesn’t matter if you pass the array as an argument or not (if you don’t explicitly pass it, it is passed by itself) . hence proved/////////

Apart from these two styles, it is worth mentioning that the following is also a valid signature for the main() method since Java 5:

public static void main(String. args) 

The method main must be declared public, static, and void. It must specify a formal parameter (§8.4.1) whose declared type is array of String.

The ellipsis . is the syntax for var-args, which can be used to pass an arbitrary number of arguments to a method. More on it here.

String args[] and String[] args are identical. In the sense that they do the same thing, Creating a string array called args.

But to avoid confusion and enforce compatibility with all other Java codes you may encounter I’d recommend using the syntax (String[] args) when declaring arrays.

One confusion you may encounter is when you try to declare multiple String array in one line, then String[] fruits, vegetables will not be the same as String fruits[], vegetables

The former creates two string arrays fruits and vegetables, while the later creates a String array of fruits and a string variable of vegetables

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What is String args[ ] in Java?

String args[] in java is an array of type java.lang.String class that stores java command line arguments. Here, the name of the String array is args (short form for arguments), however it is not necessary to name it args always, we can name it anything of our choice, but most of the programmers prefer to name it args.

We can write String args[] as String[] args as well, because both are valid way to declare String array in Java.

From Java 5 onwards, we can use variable arguments in main() method instead of String args[] . This means that the following declaration of main() method is also valid in Java : public static void main(String. args) , and we can access this variable argument as normal array in Java.

Why is String. args[] in Java Needed?

Varargs or Variable Arguments in Java was introduced as a language feature in J2SE 5.0. This feature allows the user to pass an arbitary number of values of the declared date type to the method as parameters (including no parameters) and these values will be available inside the method as an array. While in previous versions of Java, a method to take multiple values required the user to create an array and put those values into the array before invoking the method, but the new introduces varargs feature automates and hides this process.

The dots or periods( . ) are known as ELLIPSIS , which we usually use intentionally to omit a word, or a whole section from a text without altering its original meaning. The dots are used having no gap in between them.

The three periods( . ) indicate that the argument may be passed as an array or as a sequence of arguments. Therefore String… args is an array of parameters of type String, whereas String is a single parameter. A String[] will also fulfill the same purpose but the main point here is that String… args provides more readability to the user. It also provides an option that we can pass multiple arrays of String rather than a single one using String[] .

Example to Modify our Program to Print Content of String args[] in Java

When we run a Java program from command prompt, we can pass some input to our Java program. Those inputs are stored in this String args array. For example if we modify our program to print content of String args[] , as shown below:

The following Java Program demonstrates the working of String[] args in the main() method:

Compile the above program using the javac Test.java command and run the compiled Test file using the following command:

Explanation:

In the above example, we have passed three arguments separated by white space during execution using java command. If we want to combine multiple words, which has some white space in between, then we can enclose them in double quotes. If we run our program again with following command:

Conclusion

• string args[] in java is an array of type java.lang.String class that stores java command line arguments.
• Variable argument or varargs in Java allows us to write more flexible methods which can accept as many arguments as we need
• The three periods(. ) in String… args[] indicate that the argument may be passed as an array or as a sequence of arguments.
• (String… args) is an array of parameters of type String, whereas String[] is a single parameter. String[] can full fill the same purpose but just (String… args) provides more readability and easiness to use.

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Command-Line Arguments

A Java application can accept any number of arguments from the command line. This allows the user to specify configuration information when the application is launched.

The user enters command-line arguments when invoking the application and specifies them after the name of the class to be run. For example, suppose a Java application called Sort sorts lines in a file. To sort the data in a file named friends.txt , a user would enter:

When an application is launched, the runtime system passes the command-line arguments to the application’s main method via an array of String s. In the previous example, the command-line arguments passed to the Sort application in an array that contains a single String : «friends.txt» .

Echoing Command-Line Arguments

The Echo example displays each of its command-line arguments on a line by itself:

The following example shows how a user might run Echo . User input is in italics.

java Echo Drink Hot Java Drink Hot Java

Note that the application displays each word — Drink , Hot , and Java — on a line by itself. This is because the space character separates command-line arguments. To have Drink , Hot , and Java interpreted as a single argument, the user would join them by enclosing them within quotation marks.

java Echo "Drink Hot Java" Drink Hot Java

Parsing Numeric Command-Line Arguments

If an application needs to support a numeric command-line argument, it must convert a String argument that represents a number, such as «34», to a numeric value. Here is a code snippet that converts a command-line argument to an int :

int firstArg; if (args.length > 0) < try < firstArg = Integer.parseInt(args[0]); >catch (NumberFormatException e) < System.err.println("Argument" + args[0] + " must be an integer."); System.exit(1); >>

parseInt throws a NumberFormatException if the format of args[0] isn’t valid. All of the Number classes — Integer , Float , Double , and so on — have parseXXX methods that convert a String representing a number to an object of their type.

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What does «String[] args» contain in java?

It prints: [Ljava.lang.String;@153c375 and when I run it again, it prints: [Ljava.lang.String;@1d1e730 it gives me different output each time So, what does » [Ljava.lang.String;@153c375 » mean?

8 Answers 8

Update: I just realized I never answered the question «What does “String[] args” contain in java?» 🙂 It’s an array of the command-line arguments provided to the program, each argument being a String in the array.

And we now resume with our regularly-scheduled answer.

args is an array. To see individual command-line arguments, index into the array — args[0] , args[1] , etc.:

You can loop through the args like this:

For java Test one two three , that will output:

args[0]: one args[1]: two args[2]: three

Or loop like this if you don’t need the index:

So, what does «[Ljava.lang.String;@153c375» mean?

That’s Java’s default toString return value for String[] (an array of String ). See Object#toString . The [ means «array», the L means «class or interface», and java.lang.String is self-explanatory. That part comes from Class#getName() . The ;@153c375 is ;@ followed by the hashCode of the array as a hex string. (I think the default implementation of hashCode for Object indicates where in memory the array is located, which is why it’s different for different invocations of your program, but that’s unspecified behavior and wouldn’t be any use to you anyway.)

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