Introduction
In this article we discuss Varargs (Variable Arguments) in Java.
Varargs (Variable Arguments)
Varargs allow the method to accept zero, one or more arguments. Before varargs either we used an array as the method parameter or use an overloaded method, but using this causes maintenance problems. If we are not sure how many arguments will be passed in the method, then varargs is the better approach.
Advantage
Using Varargs, we don't need additional overloaded methods so less coding is used.
How Varargs Works
When initializing the arguments, the compiler starts to match the argument list left-to-right with the given parameters. Once the given set of parameters are matched, then the remaining arguments are passed as an array to the method.
Syntax
It always uses ellipsis, in other words three dots (...) after the data type. The syntax is as follows:
return_type method_name(data_type... variable_Name) {}
Example
class VarargsEx1
{
static void print(String... values)
{
System.out.println("invoked print method");
}
public static void main(String args[])
{
print();//no/zero argument
print("welcome", "to", "java", "world");//passed four arguments
}
}
Output
![fig-1.jpg]()
Another Example
class VarargsEx2
{
static void print(String... values)
{
System.out.println("invoked print method");
for(String str:values)
{
System.out.println(str);
}
}
public static void main(String args[])
{
print();//no argument passed
print("welcome");//passed only one argument
print("welcome", "to", "java", "world");//passed four arguments
}
}
Output
![fig-2.jpg]()
Rules for varargs
There are some rules for varargs that we must follow, otherwise the code can't compile. They are:
- Specify the type of the arguments (can be primitive or Object).
- Use the (…) syntax.
- You can have other arguments with varargs.
- There can be only one variable argument in the method.
- Variable arguments (varargs) must be the last argument.
A Third Example
The following example shows errors that cause the compiler to not run the program:
void method(String... str, int... b) {}// Compile time error
void method(int...a, String...str) {}// Compile time error
A Fourth Example
This example shows last the argument in the method.
class VarargsEx3
{
static void print(int n, String... values)
{
System.out.println("The no. is " +n);
for(String str:values)
{
System.out.println(str);
}
}
public static void main(String args[])
{
print(25, "hello");//only one argument
print(50, "welcome", "to", "java", "world");//passed four arguments
}
}
Output
![fig-3.jpg]()