Generic.java

// https://www.tutorialspoint.com/java/java_generics.htm

public class MyClass {
   // == 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 test1() {
      // 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
      
      // Array integerArray contains:
      // 1 2 3 4 5 
      // Array doubleArray contains:
      // 1.1 2.2 3.3 4.4 
      // Array characterArray contains:
      // H E L L O
   }



   // == 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 test2() {
      System.out.printf("\n== Largest of three Tests\n");
      System.out.printf("Max of %d, %d and %d is %d\n\n", 
         3, 4, 5, maximum( 3, 4, 5 ));

      System.out.printf("Max 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"));
         
    // Max of 3, 4 and 5 is 5
    // Max of 6.6,8.8 and 7.7 is 8.8
    // Max of pear, apple and orange is pear
   }


    // == Generic Classes
    public static class Box<T> {
       private T t;
    
       public void add(T t) {
          this.t = t;
       }
    
       public T get() {
          return t;
       }
    }

   public static void test3() {
      System.out.printf("\n== Generic Class Tests\n");
      
      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", integerBox.get());
      System.out.printf("String Value :%s\n", stringBox.get());
      
      // Integer Value :10
      // String Value :Hello World
   }

    public static void main(String args[]) {
        test1();
        test2();
        test3();
    }
}