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• Number


  An abstract class defined in the java.lang package that serves as the superclass for all numeric wrapper classes such as Integer, Double, Float, Long, Short, and Byte
• Number class


  • Provides common methods for converting numeric values to other primitive data types like int, long, float, and double
• Methods in Number class

  • intValue()
  • longValue()
  • floatValue()
  • doubleValue()
• Methods in Number class are used to obtain the corresponding primitive values of the wrapped number
• Bounded type parameters


  Used to restrict the types that can be used as type arguments in a parameterized type, e.g. a method that operates on numbers might only want to accept instances of Numbers or their subclasses
• Interfaces


  Deal with abstract data types, help in the independent manipulation of java collections from representation details, and are used to achieving multiple inheritance in java forming hierarchies
• Generic interface


  An interface that declares one or more type parameters, which act as placeholders for the actual data types that implementing classes will use
• Collection


  A framework that provides an architecture to store and manipulate the group of objects
• Java Collection


  A single unit of objects
• ArrayList


  A class that implements the List interface, uses a dynamic array to store the duplicate element of different data types, maintains the insertion order, and allows random access to the elements
• ArrayList is internally backed by the array in Java
• We cannot store primitive type in ArrayList, it stores only objects and automatically converts primitive type to object
• Array


  A basic functionality provided by Java, whereas ArrayList is a class of Java Collections framework
• ArrayList belongs to java.util package