Java Lesson Two: integers, floating-point numbers

Floating point number

The number with the decimal point. The word floating point is meant to mean that the decimal point is floating and is a way of expressing non-integers (including fractions and irrational numbers) within the computer. The other is called a fixed-point number, but no fixed-point number is encountered in Java. People use the word floating point to express all the numbers with a decimal point.

When floating-point numbers and integers are put together, Java converts integers into floating-point numbers and then operations on floating-point numbers.

A double is usually used to denote the type of floating-point number

Floating-point calculations are error-based, and integers are used when we need accurate calculations.

Integer types cannot express numbers that have fractional parts. The strange thing about a computer that has a pure integer is that it's a lot faster and takes up a little bit of space. In fact, People's daily life is still a lot of pure integer calculation, so the use of integers is still very large.

10 and 10.0 are completely different two numbers in Java.

Example: height-foot conversion, 5 ' 7 "How much is the height of the meter?

Formula: (5+7/12) *0.3048=1.7018

public class Main {public static void main (string[] args) {//TODO auto-generated method Stubint foot;int inch; Scanner in = new Scanner (system.in); foot = In.nextint (); inch = In.nextint (); System.out.println ((foot + INCH/12) *0.3048);}}

Output Result:

5 7

1.524

Why not 1.7018? Because the inch defines an int integer, and the integer operation can only get an integer, the operation INCH/12 the last rounding to 0, so the final result is wrong. On the basis of the above code, there are two methods: one is to change the INCH/12 to inch/12.0 (integer and floating-point operation results are floating-point numbers), another method is to define the inch as a floating-point number double, to the inch assignment 7, automatically into the 7.0来 participate in the operation.

Therefore, the following two kinds of code can get the correct result:

(1) inch/12.0

public class Main {public static void main (string[] args) {//TODO auto-generated method Stubint foot;int inch; Scanner in = new Scanner (system.in); foot = In.nextint (); inch = In.nextint (); System.out.println ((foot + inch/12.0) *0.3048);}}

(2) Double inch:

public class Main {public static void main (string[] args) {//TODO auto-generated method Stubint foot;double inch; Scanner in = new Scanner (system.in); foot = In.nextint (); inch = In.nextint (); System.out.println ((foot + INCH/12) *0.3048);}}

This article is from the "Office software" blog, please be sure to keep this source http://xiaobenny.blog.51cto.com/2638228/1729933

Java Lesson Two: integers, floating-point numbers