Java Identifiers
- All Java variables must be identified with unique names.
- These unique names are called identifiers.
- Identifiers can be short names (like x and y) or more descriptive names (age, sum, total).
- Names can contain letters, digits, underscores, and dollar signs.
- Names must begin with a letter.
- Names should start with a lowercase letter and it cannot contain whitespace.
- Names can also begin with $ and _.
- Names are case-sensitive ("myVar" and "myvar" are different variables)
- Reserved words cannot be used as names.
- Variables are placed in memory to storing values.
- In Java, there are different types of variables.
- For example:
- String - stores text
- int - stores integers
- float - stores floating point numbers
- char - stores single characters
- boolean - stores : true or false
- Declaring (Creating) Variables
- To create a variable, you must specify the type and assign it a value.
- Synatx:
- datatype variable_name;
- datatype variable_name = value;
- Example:
- int age;
- int age=101;
- To declare more than one variable of the same type, use a comma-separated list.
- Syntax:
- datatype var1, var2, var3,...;
- datatype var1= value1, var2=value2, var3=value3...;
- Example:
- int f1,f2,f3;
- int p1=10,p2=20,p3=30;
- Where datatype is one of Java's data types and variable_name is the name of the variable.
- The equal sign is used to assign values to the variable.
- Declaring Final Variables
- However, you can add the final keyword if you don't want others (or yourself) to overwrite existing values (read-only).
- Syntax: final datatype variable_name = value;
- Example: final int myNum = 15;
- Display Variables
- The println() method is often used to display variables.
- Example: System.out.println(myNum);
- The print() method is used to display value on same line.
- Example: System.out.print(myNum);
- To combine both text and a variable, use the + character:
- Example: System.out.println("My Number value" + myNum);
Tags:
Core java