Varargs: passing a variable number of arguments to a method

From version 5 of Java you can call a method passing a variable number of arguments.
A variable of this type is called varargs, you can only use in a method signature and its syntax is the primitive type or object type followed by 3 dots (ellipsis).
An example is the following:

package eu.lucazanini.varargs;

public class Main {

    public static void main(String[] args) {
	varargs(1, 2);
    }

    public static void varargs(int... x) {
	System.out.println("varargs");
	for (int i : x) {
	    System.out.println(i);
	}
    }
}

where the variable x is an array containing all the values ​​passed (in this example x[0] is equal to 1).
This way has some limitations:

1. you can use the variable varargs only one time in a method
2. the variable varargs must be at the last place in the method signature

As variable varargs you can pass null or no value; in the above example the call varargs() is like varargs(new int[0]) where new int[0] is an empty array but not null.

In situations of ambiguity for overloaded methods the call to method with varargs is always loser as you see from the following examples:

• example 1:

  package eu.lucazanini.varargs;
  
  public class Main {
  
      public static void main(String[] args) {
  	varargs(1, 2);
      }
  
      // not called
      public static void varargs(int... x) {
  	System.out.println("varargs");
  	for (int i : x) {
  	    System.out.println(i);
  	}
      }
  
      // called
      public static void varargs(int x, int y) {
  	System.out.println("int int");
  	System.out.println(x);
  	System.out.println(y);
      }
  }
  

• example 2 (boxing):

  package eu.lucazanini.varargs;
  
  public class Main {
  
      public static void main(String[] args) {
  	varargs(1, 2);
      }
  
      // not called
      public static void varargs(int... x) {
  	System.out.println("varargs");
  	for (int i : x) {
  	    System.out.println(i);
  	}
      }
  
      // called
      public static void varargs(Integer x, Integer y) {
  	System.out.println("Integer Integer");
  	System.out.println(x);
  	System.out.println(y);
      }
  }
  

• example 3 (widening):

  package eu.lucazanini.varargs;
  
  public class Main {
  
      public static void main(String[] args) {
  	varargs(1, 2);
      }
  
      // not called
      public static void varargs(int... x) {
  	System.out.println("varargs");
  	for (int i : x) {
  	    System.out.println(i);
  	}
      }
  
      // called
      public static void varargs(long x, long y) {
  	System.out.println("long long");
  	System.out.println(x);
  	System.out.println(y);
      }
  }