Constructor isVarArgs() method in Java with Examples

Last Updated : 29 Oct, 2019

The isVarArgs() method of java.lang.reflect.Constructor class is used to return the boolean value true if this Constructor can take a variable number of arguments as parameters else method will return false.VarArgs allows the constructor to accept a number of arguments. using VarArgs is a better approach to pass arguments than array when it is not known how many arguments to pass in the constructor.

Syntax:

public boolean isVarArgs()

Parameters: This method accepts nothing.

Return: This method returns true if and only if this executable was declared to take a variable number of arguments.

Below programs illustrate isVarArgs() method:
Program 1:

// Java program to illustrate isVarArgs() method 
  
import java.lang.annotation.Annotation; 
import java.lang.reflect.Constructor; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
        // create a class object 
        Class classObj = shape.class; 
  
        // get Constructor object 
        // array from class object 
        Constructor[] cons = classObj.getConstructors(); 
  
        // check isVargs or not 
        boolean isVargs = cons[0].isVarArgs(); 
  
        // print result 
        System.out.println("isVargs : " + isVargs); 
    } 
  
    public class shape { 
  
        public shape(Object... objects) 
        { 
        } 
    } 
} 

Output:

isVargs : true

Program 2:

// Java program to illustrate isVarArgs() method 
  
import java.lang.annotation.Annotation; 
import java.lang.reflect.Constructor; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
        // create a class object 
        Class classObj = String.class; 
  
        // get Constructor object 
        // array from class object 
        Constructor[] cons = classObj.getConstructors(); 
  
        for (int i = 0; i < cons.length; i++) { 
            // check isVargs or not 
            boolean isVargs = cons[i].isVarArgs(); 
  
            // print result 
            System.out.println(cons[i]); 
            System.out.println("isVargs : " + isVargs); 
        } 
    } 
} 

Output:

public java.lang.String(byte[], int, int)
isVargs : false
public java.lang.String(byte[], java.nio.charset.Charset)
isVargs : false
public java.lang.String(byte[], java.lang.String) throws java.io.UnsupportedEncodingException
isVargs : false
public java.lang.String(byte[], int, int, java.nio.charset.Charset)
isVargs : false
public java.lang.String(byte[], int, int, java.lang.String) throws java.io.UnsupportedEncodingException
isVargs : false
public java.lang.String(java.lang.StringBuilder)
isVargs : false
public java.lang.String(java.lang.StringBuffer)
isVargs : false
public java.lang.String(byte[])
isVargs : false
public java.lang.String(int[], int, int)
isVargs : false
public java.lang.String()
isVargs : false
public java.lang.String(char[])
isVargs : false
public java.lang.String(java.lang.String)
isVargs : false
public java.lang.String(char[], int, int)
isVargs : false
public java.lang.String(byte[], int)
isVargs : false
public java.lang.String(byte[], int, int, int)
isVargs : false

References: https://docs.oracle.com/javase/10/docs/api/java/lang/reflect/Constructor.html#isVarArgs()

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