Java Data Types

How long do primitive variables exist in memory? Define the various scopes of primitive variables?

1. Class variable (Static fields) - Class variables are variables declared within the class body, outside of any methods or blocks, and declared with 'static' keyword.Class variables have the longest scope. They are created when the class is loaded, and remain in memory as long as the class remains loaded in JVM.2. Instance variables (Non-static fields) - Instance variable are variables declared within the class body, outside of any method or block, and declared without 'static' keyword.Instance variables have the second highest scope. Instance variables are created when a new class instance is created, and live until the instance is removed from memory.3. Local Variables - Local variables are variables declared within a method body. They live only as long as the method in which it is declared remains on the stack.4. Block variables - Block variables are variables declared within a block such as an init block or within a for loop. They live only during the execution of the block and are the shortest living variables.

What is Autoboxing and Unboxing?

Autoboxing is the automatic conversion of primitive data types into their corresponding wrapper classes by Java compiler. Java compiler applies autoboxing when a primitive data type is assigned to a variable of the corresponding wrapper class, or a primitive data type is passed as an argument to a method which expects an object of the corresponding wrapper class. Unboxing is the automatic conversion of an object of a wrapper type to its corresponding primitive value by Java compiler. Java compiler applies unboxing when a wrapper object is assigned to a variable of corresponding primitive type, or when a wrapper object is passed as an argument to a method which expects corresponding primitive type.

How does Java programming language pass primitive variables to methods - by value or by reference?

In Java, primitive variables are passed to methods by value. More specifically, a copy of the primitive value is passed to the method. If the passed value changes in the method, it does not change the original value.

What is Primitive Casting in Java programming language?

Primitive Casting is used to convert primitive values from one data type to another. For example, an int value can be assigned to a float data type, or a double value can be assigned to an int data type. Casting can be either implicit or explicit. Implicit Casting: In implicit casting the conversion happens automatically, without writing specific code to do the conversion. Implicit casting happens when you convert or assign a smaller value, like a byte, to a larger data type such as an int. Explicit Casting: In explicit casting code has to be specifically written to perform the conversion from one primitive type to another. Explicit casting is done by using the syntax (data_type) where data_type is the data type that the cast is being applied to. Explicit casting happens when you convert or assign a larger value to a smaller data type.

What are Primitive Literals?

Primitive Literals are the code representation of values of primitive data types. For example 'a' is a char literal, 100 is an int literal, 'false' is a boolean literal and 2345.456 is a double literal.

What are primitive data types? What are the primitive data types supported by Java programming language?

Primitive data types are data types that are predefined in Java programming language and named by a reserved keyword. Java programming language supports eight different primitive types - byte, short, int, long, float, double, boolean and char. byte, short, int and long are integer number types. byte has 8 bits and is the smallest integer number type. long has 64 bits and is the biggest integer number type. The default value for all integer number types is 0. float and double are floating-point number types. doubles are bigger than floats. The default value for floating-point number types is 0.0 boolean has a true or false value. char contains a single, 16-bit unicode value.

What are wrapper classes in Java programming language?

There are many cases where we cannot directly use primitive data types. For example, We cannot put primitives into Java collections since Java collections (Lists, Sets etc.) can only store objects.Wrapper classes are classes provided by java programming language that enable us to wrap primitive data in Objects. int Integer char Character