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Learn Java: Variables

Let’s imagine we’re storing a user’s name for their profile. Which code example do you think is better?

String data = "Delilah";


String nameOfUser = "Delilah";

While both of these will compile, the second example is way more easy to understand. Readers of the code will know the purpose of the value: "Delilah".

Naming variables according to convention leads to clear, readable, and maintainable code. When someone else, or our future self, reads the code, there is no confusion about the purpose of a variable.

In Java, variable names are case-sensitive. myHeight is a different variable from myheight. The length of a variable name is unlimited, but we should keep it concise while keeping the meaning clear.

A variable starts with a valid letter, or a $, or a _. No other symbols or numbers can begin a variable name. 1stPlace and *Gazer are not valid variable names.

Variable names of only one word are spelled in all lowercase letters. Variable names of more than one word have the first letter lowercase while the beginning letter of each subsequent word is capitalized. This style of capitalization is called camelCase.

// good style boolean isHuman; // bad styles // no capitalization for new word boolean ishuman; // first word should be lowercase boolean IsHuman; // underscores don't separate words boolean is_human;



In the file, we declared variables with confusing names. Run the file and look at the error messages you get when trying to compile.


Some of these variable names are illegal! Change the ones that are preventing the file from compiling.

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