Usage of enum in java

The examples in this article describe the usage of enum in java. Share it with everyone for your reference. The specific analysis is as follows:

1. Basic usage
Copy the code as follows: enum Day {
SUNDAY, MONDAY, TUESDAY, WENDSDAY, THURSDAY, FRIDAY, SATURDAY;
}
Enumerations are constants, so they should be in uppercase letters.

2. Enumerations are objects

An enumeration implicitly inherits java.lang.Enum, so it has the properties and methods of java.lang.Enum. Traverse the enumeration:
Copy the code as follows: public class Main {
public static void main(String[] args) {
for(Day day:Day.values()) {
System.out.println(day);
}
}
}
3. Enumerations can have fields and methods . The following examples are from the official The Java™ Tutorials
Copy the code as follows: public enum EnumDemo {
AOBJECT("field one", "field two");

private String field1;
private String field2;

EnumDemo(String val1, String val2){
this.field1 = val1;
this.field2 = val2;
}

public void printFields(){
System.out.println(this.field1);
System.out.println(this.field2);
}

public static void main(String[] args) {
EnumDemo.AOBJECT.printFields();
}
}
The following real-life examples are from the official Java Tutorial:
Copy the code as follows: public enum Planet {
MERCURY (3.303e+23, 2.4397e6),
VENUS (4.869e+24, 6.0518e6),
EARTH (5.976e+24, 6.37814e6),
MARS (6.421e+23, 3.3972e6),
JUPITER (1.9e+27, 7.1492e7),
SATURN (5.688e+26, 6.0268e7),
URANUS (8.686e+25, 2.5559e7),
NEPTUNE (1.024e+26, 2.4746e7);

private final double mass; // in kilograms
private final double radius; // in meters

Planet(double mass, double radius) {
this.mass = mass;
this.radius = radius;
}

private double mass() { return mass; }
private double radius() { return radius; }

// universal gravitational constant (m3 kg-1 s-2)
public static final double G = 6.67300E-11;

double surfaceGravity() {
return G * mass / (radius * radius);
}

double surfaceWeight(double otherMass) {
return otherMass * surfaceGravity();
}

public static void main(String[] args) {
Double earthWeight = 120;
for(Planet p: Planet.values()){
System.out.println(p.surfaceGravity());
System.out.println(p.surfaceWeight(earthWeight/EARTH.surfaceGravity()));
}
}
}
4. Enumerations are singletons, and you can use enumerations to build a Singleton.
Copy the code as follows: public enum Singleton {
INSTANCE(new String[]{"arg1", "arg2"});

String[] myArgs;
Singleton(String[] args){
this.myArgs = args;
}

public static Singleton getInstance(){
return INSTANCE;
}

public static void main(String[] args) {
for(String arg : INSTANCE.myArgs)
System.out.println(arg);
}
}

I hope this article will be helpful to everyone’s Java programming.