I have the following enum:
public static enum OpCode { a((byte) 0x0), b((byte)0x18), c((byte)0x1A); private byte value; private OpCode (byte value) { this.value = value; } byte getValue() { return value; } if I have the value x = 0x18 how can I get the string 'b'?
this is what I tried:
System.out.println(OpCode.values()[x]); but it doesn't work
You can implement static method such as fromByte :
public enum OpCode { ... truncated public static OpCode fromByte(byte x) { for(OpCode oc : values()) { if (oc.getValue() == x) { return oc; } } throw new IllegalArgumentException("Unknown OpCode value: " + x); } } And then you can call it like this:
OpCode oc = OpCode.fromByte(x); Either linear search as Joe C suggest in its comment or use a Map to store OpCode instances by Byte value.
public static enum OpCode { a((byte) 0x0), b((byte)0x18), c((byte)0x1A); private final byte value; private final static Map<Byte, OpCode> opCodesByByte; static { opCodesByByte = new HashMap<>(); for (OpCode opCode : values()) { opCodesByByte.put(opCode.value, opCode); } } ... } And also add a static method in OpCode to provide the search method :
public static OpCode of(byte value){ return opCodesByByte.get(value); } Note that in this implementation, it returns null if no matching.
final +1
value member should also be. I updated.You need to loop the enum:
byte x = 0x18; for (OpCode opCode : OpCode.values()) { if (x == opCode.getValue()) { System.out.println(opCode); } } Alternatively, build a map like this:
private static Map<Byte, OpCode> valueToOpCode = new HashMap<>(); static OpCode getOpCode(byte value) { return valueToOpCode.get(value); } public static enum OpCode { a((byte) 0x0), b((byte)0x18), c((byte)0x1A); private byte value; private OpCode(byte value) { this.value = value; valueToOpCode.put(value, this); } byte getValue() { return value; } } private void test() { byte x = 0x18; System.out.println(getOpCode(x)); // prints 'b' } 
