Example:<\/strong><\/p>\nfor(int i = 10 ;i >= 1; i--)\n {\n \/\/ Body of for loop\n }<\/pre>\nIn the above example, int i = 10 is a declaration of a local variable i. Its scope is only limited to the \u201cfor\u201d loop.<\/p>\n
Syntax of a Local Variable:<\/strong><\/p>\nclass ClassName\n{\n methodName(){\n <DataType> localVariableName;\n localVariableName = value;\n }\n}<\/pre>\nHere, methodname is the name of the method, DataType refers to the data type of local variables like int, float, long, double, etc<\/em> and localVariableName is the name of the local variable and value is the initial value of the local variable.<\/p>\nExample:<\/strong><\/p>\ndouble area()\n {\n \tint length=10; \/\/local variable\n \tint breadth = 5; \/\/local variable\n \tdouble areaOfRectangle = length * breadth; \/\/local variable\n \treturn areaOfRectangle;\n } \/\/ scope of all local variables ends here.<\/pre>\nCode Snippet 1:<\/strong><\/p>\npublic class EmployeeSalary\n{\n public void getSalary()\n {\n long salary = 30000; \/\/declaring a local variable\n }\n public static void main(String args[])\n {\n System.out.println(\"Salary of the Employee is: \" +salary);\n }\n}<\/pre>\nOutput:<\/strong><\/p>\nException in thread “main” java.lang.Error: Unresolved compilation problem:
\nsalary cannot be resolved to a variable
\nat EmployeeSalary.main(EmployeeSalary.java:10)<\/div>\n
Reason for error:<\/strong> Accessing local variable \u201csalary\u201d outside its scope(function getSalary()) gives an error.<\/p>\nCode Snippet 2:<\/strong><\/p>\npublic class EmployeeSalary\n{\n public void getSalary()\n {\n \/\/declaring a local variable\n long salary;\n \/\/declaring and initializing local variables\n int workingDaysInAMonth = 25, salaryPerDay = 1000; salary = workingDaysInAMonth * salaryPerDay ;\n System.out.println(\"Salary of the Employee is: \" +salary);\n }\n public static void main(String args[])\n {\n EmployeeSalary employee = new EmployeeSalary();\n \/\/accessing local variable by calling method in which it is present\n employee.getSalary();\n }\n}<\/pre>\nOutput:<\/strong><\/p>\nSalary of the Employee is: 25000<\/div>\n
2. Instance Variables in Java<\/h4>\n
A variable that is declared inside the class but outside any method, constructor or block body is called an instance variable. An instance variable is a non-static variable that is, we can not declare it as static.<\/p>\n
It is called an instance variable because its value is instance-specific (related to objects) and is not shared with other instances\/objects as each object of the class has its own set of values for these non-static variables.<\/p>\n
\n- As we declare an instance variable in a class, these variables are created when an object of the class is created with the use of a \u201cnew\u201d keyword and destroyed when the object is destroyed.<\/li>\n
- We can access instance variables only by creating objects. Also, we can use these variables using the \u201cthis\u201d<\/strong> pointer inside the same class.<\/li>\n
- We can also declare instance variables with access specifiers (private, public or default). If we do not explicitly set any access specifier for the instance variables then Java assumes them as default access specifiers.<\/li>\n
- It is not necessary to initialize an instance variable. If we do not initialize it with a value, it gets a default value. We have already discussed the list of the default values of instance variables in the introductory part of the variables, in this article.<\/li>\n
- Heap Allocation is used to store the instance variables and a slot of memory is created for each instance variable value. Each object has its own copy of the instance variables that is, these variables cannot be shared among objects.<\/li>\n
- The instance variables are visible to all methods, constructors, and blocks in the class. Normally, it is recommended that we should declare the instance with a \u201cprivate\u201d access specifier.<\/li>\n<\/ul>\n
Declaration of an instance variable<\/h4>\n
We can declare instance variables inside a class. We can also declare them outside a method, block or constructor.<\/p>\n
Syntax of an Instance Variable:<\/strong><\/p>\nclass ClassName\n{\n <DataType> instanceVariableName;\n instanceVariableName = value;\n \/\/ class body\n}<\/pre>\nExample:<\/strong><\/p>\nClass AreaofShapes\n{\n \/\/These are instance variables, present inside the class\n \t\tdouble rectangleArea;\n \t\tdouble squareArea;\n \t\tdouble circleArea;\n}<\/pre>\nCode Snippet:<\/strong><\/p>\npublic class AreaOfShapes\n{\n \/\/Declaring instance variables\n double breadth;\n double length;\n double areaOfRectangle;\n double areaOfSquare;\n\n public static void main(String args[])\n {\n \/\/Creating First Object area1\n AreaOfShapes area1 = new AreaOfShapes();\n \/\/Accessing instance variables through the first object\n area1.length = 50;\n area1.breadth = 25;\n area1.areaOfRectangle= area1.length * area1.breadth;\n\n \/\/Displaying details for first object\n System.out.println(\"Details from the first object-\");\n System.out.println(\"Length of Rectangle: \" +area1.length);\n System.out.println(\"Breadth of Rectangle: \" +area1.breadth);\n System.out.println(\"Area of Rectangle: \" +area1.areaOfRectangle);\n\n \/\/Creating second Object area2\n AreaOfShapes area2 = new AreaOfShapes();\n \/\/Accessing instance variables through the second object\n area2.length = 75.5;\n area2.breadth = 68;\n area2.areaOfRectangle= area2.length * area2.breadth;\n\n \/\/Displaying details for the second object\n System.out.println(\"\\nDetails from the second object-\");\n System.out.println(\"Length of Rectangle: \" +area2.length);\n System.out.println(\"Breadth of Rectangle: \" +area2.breadth);\n System.out.println(\"Area of Rectangle: \" +area2.areaOfRectangle);\n }\n}<\/pre>\nOutput:<\/strong><\/p>\nDetails from the first object-
\nLength of Rectangle: 50.0
\nBreadth of Rectangle: 25.0
\nArea of Rectangle: 1250.0Details from the second object-
\nLength of Rectangle: 75.5
\nBreadth of Rectangle: 68.0
\nArea of Rectangle: 5134.0<\/div>\n
From the above program, it is clear that each instance (object) of the class has its own copy of the instance variable.<\/p>\n
We changed the value of instance variables using the object \u201carea2\u201d in the program but there was no effect or change in the values of the other object \u201carea1\u201d. This shows that objects have their own (separate) copy of the instance variable.<\/p>\n
3. Static Variables in Java<\/h4>\n
A variable that is declared inside a class but not inside the method, constructor or a block, with the static keyword<\/strong> is called static or class variable<\/strong>.<\/p>\nStatic variables are also called class variables because they are associated with the class and are common for all the instances of the class. That is, one copy of the static variable is shared among all objects of the class.<\/p>\n
For example, if we create multiple objects of a class and access the static variable using objects, it will be common for all, that is, the changes made to the variable using one of the objects would reflect when we access it through the other objects of the class.<\/p>\n
\n- Static variables are created at the start of program execution and get destroyed automatically after the execution of the program.<\/li>\n
- Unlike instance variables, there is only one copy of a static variable per class, irrespective of the number of objects we create from the class.<\/li>\n
- The initialization of static variables is not mandatory. If we do not initialize it with a value, it gets a default value similar to the instance variables.<\/li>\n
- Static variables can be declared as public\/private, final, and static. These variables are the constant variables that never change from their initial values.<\/li>\n
- Static memory allocation is very helpful to store the static\/class variables.<\/li>\n
- We can access the static variables by calling it with the class name, that is ClassName.variableName<\/strong>. We can also directly access the static variables inside static methods and static blocks.<\/li>\n
- The visibility of the static variable is similar to instance variables. However, we mostly declare the static variables as public, since they must be available for all objects of the class.<\/li>\n
- The values of static variables can also be assigned during the declaration or within the constructor. Also, we can assign the values in special static initializer blocks.<\/li>\n<\/ul>\n
Note:<\/strong><\/p>\n\n- If we try to access the static variable through an object, the compiler will show the warning message but will not halt the program. The compiler will automatically replace the object name with the class name.<\/li>\n
- If we access the static variable without the class name, the compiler will automatically add the class name.<\/li>\n<\/ul>\n
Syntax of a Static Variable:<\/strong><\/p>\nclass ClassName{\nstatic <DataType> <variable_name>;\n}<\/pre>\nExample:<\/strong><\/p>\nclass MyClass{\nstatic int number; \/\/number is a static variable\n}<\/pre>\nCode Snippet:<\/strong><\/p>\npublic class Student\n{\n \/\/Declaring static variables inside the class\n public static int marks;\n public static String studentName = \"John\";\n\n public static void main(String args[])\n {\n \/\/accessing static variable without creating object\n Student.marks = 80;\n System.out.println(\"The marks of student \"+Student.studentName +\"are: \"+Student.marks);\n\n \/\/creating 3 objects of the class\n Student student1 = new Student();\n Student student2 = new Student();\n Student student3 = new Student();\n\n \/\/Accessing the statc variable through objects\n System.out.println(student1.studentName);\n System.out.println(student2.studentName);\n System.out.println(student3.studentName);\n\n \/\/We can directly access the static variable like this\n System.out.println(marks);\n\n \/\/changing the value of the static variable by 1 object\n student1.studentName= \"Sam\";\n\n \/\/ change made by one object is reflected to all other objects\n System.out.println(student1.studentName);\n System.out.println(student2.studentName);\n System.out.println(student3.studentName);\n }\n}<\/pre>\nOutput:<\/strong><\/p>\nThe marks of student John are: 80
\nJohn
\nJohn
\nJohn
\n80
\nSam
\nSam
\nSam<\/div>\n
As we can see, all three objects (student1, student2, student3) displays the same output irrespective of the object (student1) through which it has been accessed. This is the reason why we can access the static variables directly without using objects like this:<\/p>\n
System.out.println(static_Variable_Name);<\/pre>\nDo note that only static variables can be accessed like this. We cannot access the instance and local variables like this!!<\/em><\/strong><\/p><\/blockquote>\nSummary<\/h3>\n
Here we came to the end of our blog on Java Variables. Now you know that variables in Java play an extremely important role in programming. They are very useful for writing programs.<\/p>\n
In this article, we have discussed the Java variables and their types in detail along with their respective examples, syntax and logical codes so that you can easily understand them. Now, you can use these Java variables in your programs flexibly.<\/p>\n
If you have any queries, do let us know with the help of the comment section below.<\/p>\n","protected":false},"excerpt":{"rendered":"
Today, in this tutorial we will get to know about the role of Variables in Java and also we will have a look at the types of Java Variables along with some examples that...<\/p>\n","protected":false},"author":1,"featured_media":76233,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[183],"tags":[1596,1597,1598,1599,1600,1601,1602],"class_list":["post-76179","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java","tag-instance-variable-in-java","tag-java-variables","tag-local-variables-in-java","tag-static-variable-in-java","tag-types-of-java-variables","tag-variables-in-java","tag-what-are-java-variables"],"yoast_head":"\n
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<\/a><\/p>\n