Everything is object
A memory:
1. Stack:
Instances of the object, basic type, etc .;
2. heap:
Store objects, class types, etc .;
3. Static storage:
Sticked the Static variable.
Data type:
Basic Type Size Minimum Value Maximum Class Type Default Boolean1-Bit - Boolean Falsechar16-Bitunicode 0Unicode 216- 1CHARACTER '/ U0000'Byte 8-BIT-128 127BYTE 0short16-Bit-215 215 - 1short 0int32-bit- 231 231 - 1integer 0long64-bit-263 263 - 1long 0LFLOAT32-BITIEEE754IEEE754FLOAT 0FDOUBLE64-BIT IEEE754IEE754DOUBLE 0DVOID --- Void Null
Note:
There are two types of types:
1) Biginteger supports an integer of any precision;
2) BigDecimal supports the floating point number of any precision.
Three scope:
1. Class data variables or object variables are not initialized, virtual opportunities assign their default values themselves;
2. Local data variables or object variables (all variables within the method) If there is no initialization, it will be wrong when compiling.
Four static keywords:
When you declare a data variable or method for static, it means that the data variable or method is not connected to any instance of the class, so you don't have to create a class's object variable, you can use Static defined data variables or method.
Note:
The data variables or methods generally defined in Static will be referred to as class variables or class methods.
