Variables a name of memory location in java
Variable is a name of memory location. In java , there are three types of variables available : local, instance and static.Variable is name of reserved area allocated in memory.
About Variable :
Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. It is a combination of two words vary and able that means its value can be changed.
Types of Variable :
There are three types of variables in java:
1. local variable
2. instance variable / non static global variable
3. static variable
1) Local Variable
A local variable is declared inside the method .
2) Instance Variable
Instance variable is declared inside the class but outside the best core java training in bangalore method. It is not declared as static.It is also known as non static global variable.
3) Static variable
A static variable is declared as static . It cannot be local.
Description about variables :
A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of the variable’s memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.
-Local variables are declared inside methods, java/j2ee classes bangalore constructors, or blocks.
- Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.
- Access modifiers cannot be used for local variables.
- Local variables are visible only within the declared method, constructor, or block.
- Local variables are implemented at stack level internally.
- There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.
- After declaration of local variable , if variable is not initialised then while using of variable we get the error. Advanced java training in bangalore
- Instance variables are declared in a class, but outside a method, constructor or any block.
- When a space is allocated for an object in the heap, a slot for each instance variable value is created.
-Instance variables are created when an object is created with the help of the keyword ‘new’ and destroyed when the object is destroyed.
-Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object’s state that must be present throughout the class.
-Instance variables can be declared in class level before or after use.
-Access modifiers can be given for instance variables. java training center bangalore
-The instance variables are visible for all methods , constructors and block in the class. Normally, it is recommended to make these variables private (access level). However, visibility for subclasses can be given for these variables with the use of access modifiers.
-Instance variables have default values. For numbers, the default value is 0, for Booleans it is false, and for object references it is null. Values can be assigned during the declaration or within the constructor.
-Instance variables can be accessed directly by calling the variable name inside the class. However, within static methods (when instance variables are given accessibility), they should be called using the fully qualified java course in bangalore name.ObjectReference.VariableName.
Class/Static Variables :
Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block.
There would only be one copy of each class variable per class, regardless of how many objects are created from it.
Static variables are rarely used other than being declared as constants. Constants are variables that are declared as public/private, final, and static. Constant variables never change from their initial value.
- Static variables are stored in the static memory. It is rare to use static variables other than declared final and used as either java /j2ee classes bangalore public or private constants.
- -Static variables are created when the program starts and destroyed when the program stops.
- -Visibility is similar to instance variables. However, most static variables are declared public since they must be available for users of the class.
- -Default values are same as instance variables. For numbers, the default value is 0; for Booleans, it is false; and for object references, it is null. Values can be assigned during the declaration or within the constructor. Additionally, values can be assigned in special static initializer blocks.
- - Static variables can be accessed by calling with the classnameClassName.VariableName.
- - When declaring class variables as public Advanced java training in bangalore static final, then variable names (constants) are all in upper case. If the static variables are not public and final, the naming syntax is the same as instance and local variables.
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