What's the Difference Between `==` and `Equals()` in Java and C#?

The difference between == and Equals() in Java and C#

When comparing two objects, there are usually two ways: using the == operator and calling the Equals/equals methods. Understanding the difference between these two methods is critical to writing accurate programs.

In Java, the == operator checks for reference equality, determining whether two objects refer to the same physical instance in memory. On the other hand, the equals method checks for equality of values, comparing properties or states of objects. This distinction is important because two objects with different references may still have equal values.

In C#, the behavior of == depends on the context. Normally, it also checks for reference equality, similar to Java. However, if an overloaded == operator is defined for the specific type being compared, it will be called, possibly achieving value equality.

In contrast, the Equals/equals methods in both Java and C# call virtual methods Object/Equals in the equals base class. This method typically checks for reference equality, but can be overridden in a derived class to provide a custom value equality check.

It is important to note that in both languages, the Equals/equals methods depend on the runtime type of the object, not the compile-time type. Additionally, attempting to call Equals/equals on a null reference will result in an exception.

Understanding the difference between == and Equals/equals is critical to writing robust code that performs correct object comparisons and equality checks.

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