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Why Object Equality in Java Isn’t Always What You Expect
- In Java, comparing objects using == checks if both variables point to the exact same object in memory, known as reference equality.
- Using new keyword creates new objects, making == return false even if objects have the same content.
- Java's string interning can reuse the same object for string literals, impacting comparison results.
- To compare object content, the equals() method is used, with built-in classes like String overriding it to compare values.
- Manual implementation of equals() is necessary for user-defined classes to compare content instead of memory references.
- Java uses equals() and hashCode() for collections like HashSet and HashMap to determine object uniqueness.
- An incorrect implementation of hashCode() can lead to issues in hash-based collections like HashMap, affecting object retrieval.
- Java handles hash collisions efficiently, allowing objects with matching hash codes but different content to coexist in collections.
- Collections like TreeMap rely on natural ordering or passed comparators, while LinkedHashSet preserves insertion order in addition to equality checks.
- Understanding object equality in Java involves considerations of how objects are compared, the type of collection used, and the implementation of equals() and hashCode().
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