Section 1 - Keywords


keyword is one of the words used to define the syntax of the Java programming language. The following are a few examples of Java keywords:

class public static void


Section 2 - Identifiers


An identifier is a valid name. Java defines the following rules for identifiers:


  • The first character must be an uppercase or lowercase letter, $, or _
  • Subsequent characters must be an uppercase or lowercase letter, $, _, or a digit
  • Identifiers may not contain punctuation or whitespace
  • Identifiers may not be the same as a keyword
  • There is no limit to the length of a Java identifier


The following are examples of valid Java identifiers:




The following are examples of invalid Java identifiers:

1hello                (identifier may not begin with a digit)
hello world        (identifier may not contain whitespace)
hello;world        (identifier may not contain punctuation)


Java is a case sensitive language: baby, BABY, and BaBy are three different identifiers.




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