Method Class | isVarArgs() Method in Java

The java.lang.reflect.Method.isVarArgs() method of Method class checks whether Method Object was declared to take a variable number of arguments or not. If the method can take a variable number of arguments then returns true otherwise it will return false.

VarArgs(variable-length arguments):

VarArgs allows method to accept a number of arguments. It is a better approach to pass arguments than array when it is not known how many arguments to pass in method.



Syntax:

public boolean isVarArgs()

Return Value: This method returns true if and only if Method has variable-length arguments else false.

Below programs illustrates isVarArgs() method of Method class:

Example 1: Below program checks GFG class methods whether Method has variable-length arguments or not. In this program a method accepts VarArgs and by isVarArgs() check method accept VarArgs or not and at last print the result.

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// Program Demonstrate isVarArgs() method
// of Method Class.
  
import java.lang.reflect.Method;
  
public class GFG {
  
    // create another method
    public static void paint(Object... values)
    {
        String message = "A Computer Science portal for geeks";
    }
  
    // create main method
    public static void main(String args[])
    {
  
        try {
  
            // get list of declared method objects of class GFG
            Method[] methods = GFG.class.getMethods();
  
            // loop through method list
            for (Method method : methods) {
  
                // check method conts VarArgs or not
                boolean isVarArgs = method.isVarArgs();
  
                // print result if VarArgs are present
                if (isVarArgs)
                    System.out.println(method + " method accepts VarArgs :"
                                       + isVarArgs);
            }
        }
        catch (Exception e) {
  
            // Print Exception if any Exception occurs
            e.printStackTrace();
        }
    }
}

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Output:

public static void GFG.paint(java.lang.Object[]) method accepts VarArgs :true

Example 2: This program is going to return all the Methods which contains variable-length arguments of class java.util.Collections.

Explanation: In this Method at first java.util.Collections Class Object is created. After creating Class Object of java.util.Collections Class a list of Method Objects is created by calling getMethods() of class Object. Iterate through Method list and get Method contains variable-length arguments using isVarArgs(). At last print Synthetic Method name.

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// Program Demonstrate isVarArgs() method
// of Method Class.
  
import java.lang.reflect.Method;
import java.util.Collections;
public class GFG {
  
    // create main method
    public static void main(String args[])
    {
  
        try {
  
            // create class object for class Collections
            Class c = Collections.class;
  
            // get list of Method object
            Method[] methods = c.getMethods();
  
            System.out.println("Methods of Collections Class"
                               + " contains VarArgs");
            // Loop through Methods list
            for (Method m : methods) {
  
                // check whether the method  contains VarArgs or not
                if (m.isVarArgs())
                    // Print Method name
                    System.out.println("Method: " + m.getName());
            }
        }
        catch (Exception e) {
            // print Exception is any Exception occurs
            e.printStackTrace();
        }
    }
}

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Output:

Methods of Collections Class contains VarArgs
Method: addAll

Reference:



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