What are the different kinds of variables in java and their uses?

Answer 1

Java is a powerful language that gives us options to have data in different forms. We have several data types that we can use for our needs. The basic data types that java offers us are termed as Primitive Data Types. Though all programming languages have varied data types java offers us with a variety of data types that are much powerful and simplified to use when compared to other languages. The Java programming language is strongly-typed, which means that all variables must first be declared before they can be used. This involves stating the variable's type and name. int age = 10; The above statement tells the java compiler that a field named "age" which holds numeric data and having an initial value of 10 is declared. A variable's data type determines the values it may contain, plus the operations that may be performed on it. In addition to int, the Java programming language supports seven other primitive data types. A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. The eight primitive data types supported by the Java programming language are: * byte: The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation. * short: The short data type is a 16-bit signed two's complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply: you can use a short to save memory in large arrays, in situations where the memory savings actually matters. * int: The int data type is a 32-bit signed two's complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else. This data type will most likely be large enough for the numbers your program will use, but if you need a wider range of values, use long instead. * long: The long data type is a 64-bit signed two's complement integer. It has a minimum value of -9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive). Use this data type when you need a range of values wider than those provided by int. * float: The float data type is a single-precision 32-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion. As with the recommendations for byte and short, use a float (instead of double) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to use the java.math.BigDecimal class instead * double: The double data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency. * boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined. * char: The char data type is a single 16-bit Unicode character. It has a minimum value of '\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive). In addition to the eight primitive data types listed above, the Java programming language also provides special support for character strings via the java.lang.String class. Enclosing your character string within double quotes will automatically create a new Stringobject; For ex: String name = "Rocky"; would create a new String object of name "name" and holding an initial value "Rocky" String objects are immutable, which means that once created, their values cannot be changed. The String class is not technically a primitive data type, but considering the special support given to it by the language, you'll probably tend to think of it as such. Default Values It's not always necessary to assign a value when a field is declared. Fields that are declared but not initialized will be set to a reasonable default value by the compiler. Generally speaking, this default will be zero or null, depending on the data type. Relying on such default values, however, is generally considered bad programming style. The default values for the primitive data types are: 1. byte - 0 2. short - 0 3. int - 0 4. long - 0L 5. float - 0.0f 6. double - 0.0d 7. char - '\u0000' 8. String or any other object - null 9. boolean - false These default values are assigned only to class level variables or class instance variables. Local variables are slightly different; the compiler never assigns a default value to an uninitialized local variable. If you cannot initialize your local variable where it is declared, make sure to assign it a value before you attempt to use it. Accessing an uninitialized local variable will result in a compile-time error.