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Message: <blockquote data-quote="D_Mad" data-source="post: 20585265" data-attributes="member: 476938">Variable Declarations In our trivial HelloWorld program, we printed a message to the console that cannot be modified by the application user. What if you want to print a greeting to the user? In other words, suppose you want to ask the user her name and print the message “Hello” along with her name. In such situations, you need to accept and store the user’s name somewhere in the program and then later on output it to the console. That’s where you need to have variables in your code. A variable is of a particular data type like primitive data types we discussed earlier, or it may be of a nonprimitive class type, which we will be using in several examples in the book. A variable holds data assigned to it for a certain duration of the application run. In the current situation, you may create a variable called name of the String or Char array data type, ask the user to input her name, and store it in this variable. After the greeting message is printed, the variable may be destroyed. The value assigned to a variable may change on each run or several times within the same run. You need variables for several reasons, such as performing mathematical computations, storing and retrieving data, creating and displaying graphics, and so on. Because you may be creating several variables in a typical application, it is important that you also control their lifetime. Note that each variable occupies a definite storage space in memory, and if you create a variable that lives throughout the life cycle of your application, your program will consume a lot of memory resources during its run. You should create a variable as and only when it is required and destroy it after its use. This will help you conserve precious memory resources. You will learn how to do this in the section on scoping variables later in this syntax reference. Let’s now discuss how to create and use variables in your Java programs. You create variables in Java using the identifiers discussed in the previous section. The following declaration creates a variable called name of type String that can hold string values assigned to it: String name; A variable declaration such as int customerID; holds an integer value. Here are a few more examples of variable declarations and why they are valid or invalid: _sysadmin __myaccount x FFEE Output_sum#amount Output sum#amount 1stMember double // // // // // // // // // a variable name can start with an underscore the underscore character is allowed in any place a variable can consist of a single character a variable can consist of all uppercase alphabets a variable can contain special characters such as a pound sign (#) invalid due to the space character invalid as first letter cannot be a digit invalid as this is a reserved word Tip All identifier declarations in your program code should follow standard naming conventions. Naming conventions make programs easier to read, thus making them more understandable. The convention for declaring variables in Java is that a variable name should use mixed case with a lowercase first alphabet. Internal words start with an uppercase. It is recommended that variable names not start with an underscore and a dollar sign, even though both are allowed characters. The names should be short yet meaningful. One-character names should be avoided except for temporary throwaway variables. Use i, j, k, m, and n for temporary integer declarations; use c, d, and e for characters. Having discussed so much theory, let’s jump into some coding again. The programming example that follows asks the user to input her name and then prints a greeting message containing the name to the console. You will learn how to accept user input in your program code. After this little bit of hands-on practice, we will cover more theory on variable scoping and constants declarations in Java before concluding this syntax reference. </blockquote>

Verification: Hath warak paha keeyada? (hatha wadikireema paha)

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