java basic data types Tips

Data type of expansion

Processing banking

Speaking of numbers, we may first think of int, float data types

But for "money", the use of floating-point data type is not enough, Int is not

Why not float?

• Because the float double float is limited, discrete, rounding errors, approximately, close but not equal
• When we deal with these data require precision floating-point numbers should be avoided

float f=0.1f;    //0.1
double d=1.0/10;   //0.1
System.out.println(f==d);   //false
float d1=2212121454554f;
float d2=d1+1;
System.out.println(d1==d2)   //true
    

Visible when using the float it is inaccurate to compare

So, what data should be processed banking?

Using mathematical tools java BigDecimal

Type Conversion

int i=128;

byte b=(int)i;  //由高到低   强制转换
double b=i;     //由低到高   自动转换