Question

Is it OK to use == on enums in Java, or do I need to use .equals()? In my testing, == always works, but I’m not sure if I’m guaranteed of that. In particular, there is no .clone() method on an enum, so I don’t know if it is possible to get an enum for which .equals() would return a different value than ==.

For example, is this OK:

public int round(RoundingMode roundingMode) {   if(roundingMode == RoundingMode.HALF_UP) {     //do something   } else if (roundingMode == RoundingMode.HALF_EVEN) {     //do something   }   //etc } 

Or do I need to write it this way:

public int round(RoundingMode roundingMode) {   if(roundingMode.equals(RoundingMode.HALF_UP)) {     //do something   } else if (roundingMode.equals(RoundingMode.HALF_EVEN)) {     //do something   }   //etc } 

Answer 1

Just my 2 cents: Here is the code for Enum.java, as published by Sun, and part of the JDK:

public abstract class Enum<E extends Enum<E>>     implements Comparable<E>, Serializable {      // [...]      /**      * Returns true if the specified object is equal to this      * enum constant.      *      * @param other the object to be compared for equality with this object.      * @return  true if the specified object is equal to this      *          enum constant.      */     public final boolean equals(Object other) {          return this==other;     }   }