A good memory is better than a bad pen. 1-java basic data types and conversions

First, the basic data type

1 , Boolean (Boolean)

Boolean (Boolean): True/false, can not be replaced by 0 or not 0, cannot be converted between data.

2 , Integer type

The integer default is int , and a long type represents a range that is larger than the int table, 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

longl2=8888888888;// The value is outside the int range, error occurs

longl3=8888888888l;// correct

3 , floating-point types

floating-point type defaults to double, so the float type declaration needs to be f/f later, or with a cast character.

Float and double , float is a 4-byte precision; a double is a 8-byte precision

float f1= (float) 0.1;

Float f2=0.1f;

F1 is a eight-byte double type that is cast to a four-byte float type.

F2 itself is a four-byte float type.

4 , character type (char)

Each character occupies two bytes;

Second, the basic data type conversion

The data types are arranged by capacity size (number of table range size) from small to large:

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

1. principles to be followed during conversion

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

2 when a large-capacity type is converted to a small capacity type, the conversion must be strengthened;

3 ) byte, the Short,char does not convert to each other, and the three are first converted to the int type at the time of calculation;

4 The real number constant defaults to the double type, and the integer constant defaults to the int type;

5 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. Basic Data type Conversion sample

Int i1=223;

Int i2=446;

Double D1 = (I1+I2) *1.2// types with small capacity are automatically converted to large capacity types

Float f1 = (float) (I1+I2) *1.2// when a large-capacity type is converted to a small-capacity type, you need to add a cast character

Byte b1=1;

Byte b2=2;

byte b3= (byte) (B1+B2); Byte,Short, char is converted to int at the time of calculation, and the conversion character is enhanced when the bulk (int) is converted to a small-capacity type (byte)

A good memory is better than a bad pen. 1-java basic data types and conversions