variable

Variable overview

Variables must have clear types, what types of variables are installed in what types of data.

Basic types in 8: byte, short, int, long, float, double, char, Boolean

Define variable syntax format:

Data type variable name = data value;

Precautions for the use of variables: I: variables can be assigned without assignment after they are fixed, and they can be assigned again when they are used. Cannot be used without assignment.

2： There are scope restrictions when using variables.

Data type conversion

operator

① Arithmetic operator:

+It is converted to a string only when it is added directly to the string.

② Assignment operator:

③ Comparison operator:

Note the difference between the = sign in the assignment operator and the = = sign in the comparison operator.

④ Logical operators:

Short circuit & &: the data on both sides involved in the operation is false, then the operation result is false;

Short circuit or |: if the data on both sides involved in the operation is true, the operation result is true.

⑤ Ternary operator:

(conditional expression)? Expression 1: expression 2;