Java - Generics

public class GenericMethodTest
{
   // generic method printArray                         
   public static < E > void printArray( E[] inputArray )
   {
      // Display array elements              
         for ( E element : inputArray ){        
            System.out.printf( "%s ", element );
         }
         System.out.println();
    }

    public static void main( String args[] )
    {
        // Create arrays of Integer, Double and Character
        Integer[] intArray = { 1, 2, 3, 4, 5 };
        Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };
        Character[] charArray = { 'H', 'E', 'L', 'L', 'O' };

        System.out.println( "Array integerArray contains:" );
        printArray( intArray  ); // pass an Integer array

        System.out.println( "\nArray doubleArray contains:" );
        printArray( doubleArray ); // pass a Double array

        System.out.println( "\nArray characterArray contains:" );
        printArray( charArray ); // pass a Character array
    } 
}

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Array integerArray contains:
1 2 3 4 5 6

Array doubleArray contains:
1.1 2.2 3.3 4.4 

Array characterArray contains:
H E L L O

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Example:

public class MaximumTest
{
   // determines the largest of three Comparable objects
   public static <T extends Comparable<T>> T maximum(T x, T y, T z)
   {                      
      T max = x; // assume x is initially the largest       
      if ( y.compareTo( max ) > 0 ){
         max = y; // y is the largest so far
      }
      if ( z.compareTo( max ) > 0 ){
         max = z; // z is the largest now                 
      }
      return max; // returns the largest object   
   }
   public static void main( String args[] )
   {
      System.out.printf( "Max of %d, %d and %d is %d\n\n", 
                   3, 4, 5, maximum( 3, 4, 5 ) );

      System.out.printf( "Maxm of %.1f,%.1f and %.1f is %.1f\n\n",
                   6.6, 8.8, 7.7, maximum( 6.6, 8.8, 7.7 ) );

      System.out.printf( "Max of %s, %s and %s is %s\n","pear",
         "apple", "orange", maximum( "pear", "apple", "orange" ) );
   }
}

						

Maximum of 3, 4 and 5 is 5

Maximum of 6.6, 8.8 and 7.7 is 8.8

Maximum of pear, apple and orange is pear

						
Example:

public class Box<T> {

  private T t;

  public void add(T t) {
    this.t = t;
  }

  public T get() {
    return t;
  }

  public static void main(String[] args) {
     Box<Integer> integerBox = new Box<Integer>();
     Box<String> stringBox = new Box<String>();
    
     integerBox.add(new Integer(10));
     stringBox.add(new String("Hello World"));

     System.out.printf("Integer Value :%d\n\n", integerBox.get());
     System.out.printf("String Value :%s\n", stringBox.get());
  }
}

						

Integer Value :10

String Value :Hello World