Study Notes for dark horse programmers

Watch the video: 011 _ identifier _ programmer _ Java basic video. Avi

Basic Components of Java

Keywords, identifiers, comments, constants and variables, operators, statements, functions, and arrays.

 

Keywords

 

 

Identifier

1. Some custom names in the program

2. It consists of 26 English letters (uppercase/lowercase), numbers, and 0-9 Characters: _ $.

3. Rules defining valid identifiers:

A. numbers cannot start

B. You cannot use keywords.

4. Strictly case sensitive in Java

5. Note: when naming a name, try to give it a meaningful name.

 

 

 

Watch video: 012 _ constant _ dark horse programmer _ Java basic video

Constants and variables

Classification of constants in Java:

1. integer constant, all certificates

2. Decimal constant, all decimal places

3. boolean constants, which are special and only have two values: true and false.

4. character constants. Use single quotes ('') to mark a number, letter, or symbol

5. string constants. Mark multiple characters with double quotation marks

6. null constant. Only one value is null.

 

For integers: Java has three forms

Decimal: 0-9, full 10 into 1

Octal: 0-7, full 8 into 1, starting with 0

Hexadecimal: 0-9, A-F, full 16 into 1, starting with 0x.