Dark Horse Programmer--identifiers, keywords, constants, variables, ternary operators

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First, identifiers

　　1, consisting of letters, numbers, underscores, and the first must be a letter or underline

2. Case-sensitive in C, keyword cannot be used as identifier

Second, the key word　

Definition: A word that is given special meaning by Java.

Features: The expression is English lowercase.

Three, constant

Definition: A fixed value in Java that represents an immutable number.

Categories of Constants in Java:

1, integer constant. All integers.

2, decimal constant. All decimals.

3, Boolean constant. More unique, only two values. True false.

4, character constant. A numeric letter or symbol is identified by a single quotation mark (' ').

5, string constant. Identifies one or more characters in double quotation marks ("").

The 6,null constant. There is only one value: null.

Iv. variables　　

Concept: A storage space in memory. Has its own name (variable name) and type (data type).

Function: It is used to keep the same type of data, and can be reused.

Define the format of the variable: data type variable name = initialization value;

automatic promotion of type:

In operations, when low-type data is computed with high-type data, the system automatically promotes the low-type data in the expression to a high type. Such as:

byte B = 3; int C;

C= B + 2; b automatically promotes the operation of the int type.

Five or three-tuple operator

Ternary operators

Format:

(conditional expression)? Expression 1: Expression 2;

A) If the condition is true, the result of the operation is an expression of 1;

b) If the condition is false, the result of the operation is an expression of 2;

Example:

Gets the large number of two numbers.

int x=3,y=4,z;

z = (x>y)? The x:y;//z variable stores a large number of two numbers.

Dark Horse Programmer--identifiers, keywords, constants, variables, ternary operators