Map.get() Behaviour for objects with an equals() override
So my object is basically a few variables, which I compare in an equals() overridden method.
When I my map contains an object like
{ myvar = 1; othervar = "Hello"; yetanother= 12.4f }
and I map.get(new MyObject(1, "Hello", 12.4f) with an unrelated but content wise identical object, would it get the entry for the original object?7 Replies
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equals() and hashCode() methods are implemented correctly, yes.
Do not override equals() without also overriding hashCode(), and use the same member fields to calculate the hash code/equality, otherwise your Map may behave really funky. 🙂
(Also, it would have been really easy to simply try this out.)Thanks, I guess you'Re right about trying, but I would have just noticed it didn't work because I didn't know about also overwriting the hashCode
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right, but it would have changed your question. 🙂 The requirement to override both methods is mentioned in the documentation of Object, and Map mentions it as well: https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Map.html
Map (Java SE 21 & JDK 21)
declaration: module: java.base, package: java.util, interface: Map
Object (Java SE 21 & JDK 21)
declaration: module: java.base, package: java.lang, class: Object
Your IDE might also give you a warning, if you override only one of the methods, but that (of course) depends on your IDE and its configuration.
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