Menu
Can one assign custom numeric values to enum elements in Java? Not directly as you've written, i.e., where an enum value equals a number, but yes indirectly as shown in Ben S's link.
If values are not assigned to enum members, then the compiler will assign integer values to each member starting with zero by default. The first member of an enum will be 0, and the value of each successive enum member is increased by 1. You can assign different values to enum member.
No, we can have only strings as elements in an enumeration. Using strings in it, generates a compile time error.
You cannot create an object of an enum explicitly so, you need to add a parameterized constructor to initialize the value(s). The initialization should be done only once. Therefore, the constructor must be declared private or default. To returns the values of the constants using an instance method(getter).
public enum EXIT_CODE {
A(104), B(203);
private int numVal;
EXIT_CODE(int numVal) {
this.numVal = numVal;
}
public int getNumVal() {
return numVal;
}
}
Yes, and then some, example from documentation:
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);
// in kilograms
private final double mass;
// in meters
private final double radius;
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) {
if (args.length != 1) {
System.err.println("Usage: java Planet <earth_weight>");
System.exit(-1);
}
double earthWeight = Double.parseDouble(args[0]);
double mass = earthWeight/EARTH.surfaceGravity();
for (Planet p : Planet.values())
System.out.printf("Your weight on %s is %f%n",
p, p.surfaceWeight(mass));
}
}
Assuming that EXIT_CODE is referring to System . exit ( exit_code ) then you could do
enum ExitCode
{
NORMAL_SHUTDOWN ( 0 ) , EMERGENCY_SHUTDOWN ( 10 ) , OUT_OF_MEMORY ( 20 ) , WHATEVER ( 30 ) ;
private int value ;
ExitCode ( int value )
{
this . value = value ;
}
public void exit ( )
{
System . exit ( value ) ;
}
}
Then you can put the following at appropriate spots in your code
ExitCode . NORMAL_SHUTDOWN . exit ( ) '
Extending Bhesh Gurung's answer for assigning values, you can add explicit method to set value
public ExitCode setValue( int value){
// A(104), B(203);
switch(value){
case 104: return ExitCode.A;
case 203: return ExitCode.B;
default:
return ExitCode.Unknown //Keep an default or error enum handy
}
}
From calling application
int i = 104;
ExitCode serverExitCode = ExitCode.setValue(i);
//You've valid enum from now
[Unable to comment to his answer, hence posting it separately]
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With