Java Learning---2.java basics

1, a variable is a small area in memory that uses the variable name to access the area.

2. Local variables are set to the initial value, first declared in the assignment

3. Process of program execution:

3. Type conversion: The small size of the type automatically converted to a large capacity data type, byte short char does not convert to each other, the calculation is first converted to int type, large conversion to small to strengthen the conversion

byte b3= (Byte) (B1+B2)

Double d2=1e200;

float f2= (float) d2;//will generate overflow

Float f3=1.23f;//must add f

Long l2=300000000l;//must add L, otherwise the compiler thinks it is int, must add l

Java Learning---2.java basics