Analysis of the principle example of Java Number Class
This article introduces the relevant knowledge of "Java Number class principle instance analysis". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!
Number class
Built-in data types: byte, int, long, double, etc.
Wrapper classes: Integer, Long, Byte, Double, Float, Short,
This wrapper, which is particularly supported by the compiler, is called boxing, so when the built-in data type is used as an object, the compiler boxing the built-in type as a wrapper class. Similarly, the compiler can unbox an object into a built-in type. The Number class belongs to the java.lang package.
Public class Test {public static void main (String args []) {Integer x = 5; x = x + 10; System.out.println (x);}}
When x is assigned an integer value, the compiler boxed x because it is an object. Then, in order to enable x to add, it is necessary to unbox x
Number class methods:
The xxxValue method: converts the Number object to a value of the xxx data type and returns
Public class Test {public static void main (String args []) {Integer x = 5; / return byte native data type System.out.println (x.byteValue ()); / 5 / return double native data type System.out.println (x.doubleValue ()); / / 5.0 / return long native data type System.out.println (x.longValue ()); / / 5}
CompareTo () method: compare number objects with parameters and compare two data of the same type
Returns 0 if the specified number is equal to the parameter. Returns-1 if the specified number is less than the parameter. Returns 1 if the specified number is greater than the parameter.
Public class Test {public static void main (String args []) {Integer x = 5; System.out.println (x.compareTo (3)); / / 1 System.out.println (x.compareTo (5)); / / 0 System.out.println (x.compareTo (8)); / /-1}}
Equals () method: determines whether the number object is equal to the parameter
Integer x = 5; Integer y = 10; Integer z = 5; Short a = 5; System.out.println (x.equals (y)); / / false System.out.println (x.equals (z)); / / true System.out.println (x.equals (a)); / / false
ValueOf () method: returns the native Number object value of a given parameter, which is a static method
Integer x = Integer.valueOf (9); / 9 Double c = Double.valueOf (5); / 5.0 Float a = Float.valueOf ("80"); / / 80.0 Integer b = Integer.valueOf ("444,16); / / use hexadecimal / / 1092
The toString () method: returns a value as a string
System.out.println (x.toString ()); System.out.println (Integer.toString (12))
Parselnt (): parses a string to an int type
Int x = Integer.parseInt ("9"); double c = Double.parseDouble ("5"); int b = Integer.parseInt ("444", 16)
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