Keywords: computer languages previously defined, have special significance identifier.
A total of 50 keywords, use can be divided into the following four categories:
1. A data type;
boolean、byte、char、 double、 false、float、int、long、new、short、true、void、instanceof。
2. For statement;
break、case、 catch、 continue、 default 、do、 else、 for、 if、return、switch、try、 while、 finally、 throw、this、 super。
3. For the modification;
abstract、final、native、private、 protected、public、static、synchronized、transient、volatile。
4. For the methods, classes, interfaces, packages, and abnormal.
class、 extends、 implements、interface、 package、import、throws。
Reserved words: In the new version of the JDK can be promoted to the keyword.
Identifier: programmer when defining Java program, custom some names.
Naming rules:
1. uppercase and lowercase letters, numbers, underscores, dollar symbols;
2. Do not start with a number, not a keyword;
3. strictly case-sensitive;
4 can be any length.
Precautions:
1. folder (that package): all lowercase;
2. The class or interface:
A word: the first letter must be uppercase, such as: Student, Dog
More than one word: the first letter of each word must be capitalized, such as: HelloWorld, StudentName
The method or a variable:
A word: the first letter lowercase, such as: main, age, sex
More than one word: from the beginning of the second word, the first letter of each word in lowercase, such as: studentAge, showAllNames ()
4. constants:
A word: all caps, such as: PI
More than one word: all uppercase, but between words separated by underscores, such as: STUDENT_MAX_AGE