1 Enum quang trọng thứ tự trong khai báo

 nó sẽ quy định ra get ra cái gì 

2) Sort 

3 Rounding value in java

3.1 Rounding value number

float down = 5.3f;
float mid = 5.5f;
float up = 5.7f;

Math.ceil(a): Rounding number min value >= a , Rounding up

 // ceil rounding up return double
System.out.println(Math.ceil(down)); //6.0
System.out.println(Math.ceil(mid)); //6.0
System.out.println(Math.ceil(up)); //6.0

Math.floor(a): Rounding number max value <= a, Rouding down

 // floor rounding down return double
System.out.println(Math.floor(down)); //5.0
System.out.println(Math.floor(mid)); //5.0
System.out.println(Math.floor(up)); //5.0

Math.round(a): Rounding number value near a

 // round
System.out.println(Math.round(down)); //5
System.out.println(Math.round(mid)); //6
System.out.println(Math.round(up)); //6

 3.2 Rouding number Bigdecimal Use bigdecimal.setScale(scale, ModeRounding)

3.3 Rounding number Double use DecimalFormat and set setRoundingMode

Github: https://github.com/nguyenthinhit996/sharefullcode/blob/master/Learn%20Java/Java%20Basic/Number/src/numbers/RoundingValue.java