Create a class named Rock that acts as a superclass for rock samples collected and
catalogued by a natural history museum. The Rock class contains fields for a number
of samples, a description of the type of rock, and the weight of the rock in grams.
Include a constructor that accepts parameters for the sample number and weight.
The Rock constructor sets the description value to Unclassified. Include get methods
for each field. Create three child classes named IgneousRock, SedimentaryRock, and
MetamorphicRock. The constructors for these classes require parameters for the
sample number and weight. Search the Web for a brief description of each rock type
and assign it to the description field. Create an application that instantiates an object
of each type and demonstrate that the methods work appropriately. Save the files as
Rock.java, IgneousRock.java, SedimentaryRock.java, MetamorphicRock.java,
and DemoRocks.java.