Basic data types and conversions between Java basics

1. Boolean (Boolean): True/false, can not be replaced by 0 or not 0, the conversion between data is not possible.

2. Integer type

* * The integer type defaults to int, and a long type represents a range that is larger than the INT table number, so when a long type is declared, the constant is added with L (l).

such as: Long l1=12345678//value within the range of int, no error

Long l2=8888888888;//value is outside the int range, error occurs

Long l3=8888888888l; That's right

3. Floating-point type:

* Floating-point type is double by default, so the float type declaration needs to be f/f later or with a cast character.

float f1= (float) 0.1;

Float f2=0.1f;

The difference between the two: F1 is a eight-byte double type, cast to a four-byte float type.

The F2 itself is a four-byte float type.

4. Character type (char)

Each character occupies two bytes; The value is placed in the "";

Second, the basic data type conversion:

Each data type is arranged by size (size of table) from small to large:

Byte, Short, char--int--long--float--double

1. Principles to be followed when converting:

1) The type of small capacity is automatically converted to the type of capacity;

2) If the type with large capacity is converted to a small capacity type, the conversion character should be strengthened;

3) The Byte,short,char does not convert to each other, and the three are first converted to the int type when calculating;

4) The literal constant defaults to the double type, and the integer constant defaults to the int type;

* Why can the character type and the shaping, floating-point type of operation?

Answer: The character type is also a number inside the machine. When the calculation is performed, the asck code of the character is obtained before the calculation.

2. Conversion Example:

Int i1=123;

Int i2=456;

Double D1 = (I1+I2) *1.2//small size type automatically converted to a large capacity type

Float F1 = (float) (I1+I2) *1.2///large size type when converting to a small capacity type, you need to add the cast character

Byte b1=1;

Byte b2=2;

byte b3= (Byte) (B1+B2); Byte,short,char conversion is enhanced when the calculation is first converted to int, and large capacity (int) is converted to a small-capacity type (byte)

Basic data types and conversions between Java basics