Question

22. Define a generic method which takes as parameters (1) a reference to an object of a generic type and (2) an array of references to that generic type. Your method must loop through the array, and for the first reference in the array which is null, assign that reference to point to the same object as the reference parameter, then return. The method should have void as its return type.

Answer 1

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JAVA PROGRAM

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/////////////////////GenericTest.java/////////////////////////////

/**
* Class: GenericTest
* Purpose: To test theGenericMethod as defined
* @param <E>
*/
public class GenericTest<E> {
   //main mehtod to test theGenericMethod
   public static void main(String[] args){
       System.out.println("Test1: Testing generic method on type Integer..");
       //create GenericTest instance of Integer
       GenericTest<Integer> test1 = new GenericTest<Integer>();
       Integer intArr[] = new Integer[5]; //declare an intArr with capacity of 5
       //assign first 3 integers
       intArr[0] = 10;
       intArr[1] = 20;
       intArr[2] = 30;
       Integer theInt = 40; //reference integer
       test1.print(intArr); //print the original integer array
       System.out.println("Calling theGenericMethod for Integer... ");
       test1.theGenericMethod(theInt, intArr); //call generic method
       test1.print(intArr);//again print the changes contents of the array
      
       System.out.println("-----------------------------");
      
       System.out.println("Test2: Testing generic method on type String..");
       //create GenericTest instance of String
       GenericTest<String> test2 = new GenericTest<String>();
       String strArr[] = new String[5];//declare a strArr with capacity of 5
       //assign first 2 strings
       strArr[0] = "Apple";
       strArr[1] = "Banana";
       String theStr = "Mango"; //reference String
       test2.print(strArr); //print the original String array
       System.out.println("Calling theGenericMethod for String... ");
       test2.theGenericMethod(theStr, strArr);//call generic method
       test2.print(strArr);//again print the changes contents of the array
      
   }
  
   /**
   * this method is an additional method
   * to print the contents of the generic array
   * @param arr
   */
   public void print(E[] arr){
       System.out.println("The elements in array: ");
       for(E item: arr){
           System.out.print(item+" ");//print item
       }
       System.out.println();
   }
  
   /**
   * theGenericMethod takes as parameters (1) refObject of a generic type
   * and (2) theGenericArr generic type array.
   * The method must loop through the array, and for the first reference
   * in the array which is null, assign refObject to point to the same object
   * as the reference parameter, then return.
   * @param refObject
   * @param theGenericArr
   */
   public void theGenericMethod(E refObject,E[] theGenericArr){
       //traverse through theGenericArr
       for(int i = 0; i < theGenericArr.length; i++){
           E currentObj = theGenericArr[i];//get current item in array
           if(currentObj == null){ //if it is null
               theGenericArr[i] = refObject; //assign refObject to that index of array
               return;
           }
       }
   }

}

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OUTPUT

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Test1: Testing generic method on type Integer..
The elements in array:
10 20 30 null null
Calling theGenericMethod for Integer...
The elements in array:
10 20 30 40 null
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Test2: Testing generic method on type String..
The elements in array:
Apple Banana null null null
Calling theGenericMethod for String...
The elements in array:
Apple Banana Mango null null