In programming languages, identifiers are used for identification purposes. In Java, an identifier can be a class name, method name, variable name, or label. For example: @luka That`s exactly why I asked which language@Tony In all languages taught here at SL, it is legal to start an identifier with an underscore _. It may not be the convention, but it is legal. (As for PHP, of course, I look at the first character after the $, since it`s the actual identifier that $ simply means it`s a variable) Which of the following are not allowed to use Java identifiers? @Tony The question itself is wrong. Especially since no language is provided. Just because someone asks a question that offers multiple choices and tells you that 4 of them are right or wrong doesn`t mean it`s true, which isn`t the case in this case. @ChaoticDawg docs.oracle.com/javase/tutorial/java/nutsandbolts/variables.html yes, it`s legal, but in his case he needs 4 illegals, we can`t just drop VAC, can we!? while the other 3 are guaranteed false. 1alpha = illegal number before alpha , _abcd = illegal because starting with non-alpha, xy+abc = illegal variable must not contain “+”, transient = illegal because a keyword , acc = legal Variable names are case sensitive. The name of a variable can be any legal identifier: an unlimited sequence of Unicode letters and numbers, beginning with a letter, the dollar sign “$” or the underscore “_”. However, the convention is to always start your variable names with a letter, not “$” or “_”. Also, by convention, the dollar sign is not used at all. There may be situations where auto-generated names include the dollar sign, but your variable names should always avoid it.
A similar convention applies to underscores. Although it is technically legal to start the name of your variable with “_”, this approach is not recommended. Spaces are not allowed. Ending characters can be letters, numbers, dollar signs, or underscores. Convention (and common sense) also apply to this rule. When choosing a name for your variables, use full words instead of cryptic abbreviations. This will make your code easier to read and understand. In many cases, your code will also become self-documented. For example, fields called cadence, speed, and speed are much more intuitive than abbreviated versions like S, C, and G. Also note that the name you choose cannot be a keyword or a reserved word. If the name you choose is just a word, write it in lower case. If it consists of more than one word, capitalize the first letter of each subsequent word.
The names gearRatio and currentGear are great examples of this convention. If your variable stores a constant value, such as the static final value int NUM_GEARS = 6, the convention changes slightly, with each letter uppercase and subsequent words separated by the underscore. By convention, the underscore is not used anywhere else. In the Java code above we have 5 identifiers, namely: @ChaoticDawg: LOL, ok ok, it`s just a variable, let`s find another topic, I said it was fine with the underscore, but preferably not for some cases, it could be considered a space or a space and cannot be called (based on the application development site too). A. is the correct answer. Although it is not used anywhere in Java code, it has been kept as a reserved word to prevent its use in any form. Note: The const and goto keywords are reserved, even if they are not currently used.
Instead of const, the last keyword is used. Some keywords, such as strictfp, are included in later versions of Java. Which language? In Java: a. 1alpha = no, the identifier cannot start with a numeric value b. _abcd = yes c. xy+abc = no, cannot use the + operator in the identifier d. transient = non-transient is a reserved keyword e. acc = yes It cannot be identical to Java keywords or literals (i.e. true, false, or null). A valid Java identifier consists of a sequence of Java letters and numbers. For option C. Yes, this is valid.
This is a valid statement: String String = “String”; Java letters include Latin ASCII letters in uppercase and lowercase, and _ , $. For option F. There is no limit to the length of an identifier. There are certain rules for defining a valid Java ID. These rules must be followed, otherwise we will get a compilation error. These rules also apply to other languages such as C,C++. If it`s a challenge for solo learners, you can post it in the Quiz Factory. Each programming language reserves a few words to represent the features defined by that language. These words are called reserved words. They can be briefly divided into two parts: keywords(50) and literals(3). Keywords define functionality and literals define a value.
Identifiers are used by symbol tables in different phases of parsing (such as lexical, syntax, semantics) of a compiler architecture. In fact, class names can serve as valid identifiers, as in `String` in one of the options above. For option D. An identifier can begin with a _ sign or a $ sign.