C what is the difference between a.equals(b) and a == b

To avoid this verification in future, please log in or register. Your comment on this answer: Email me at this address if a comment is added after mine: Email me if a comment is added after mine Privacy: Your email address will only be used for sending these notifications. Your answer. Privacy: Your email address will only be used for sending these notifications. This implementation also calls Equals on pairs of references within the two values being compared.

Here is a great blog post about WHY the implementations are different. Equals is going to be dynamically bound at runtime. Equals is to check value. Equals b are both holding identical values? With one exception: For string and predefined value types such as int , float etc.. The reason this matters is that you can do this:. At a simple level, the difference is which method is called. Equals call will do a virtual dispatch on the. Equals method. As to what the particular methods do, it's all in the code.

Ideally this methods should be equivalent sorry for the pun and have the same output but it is not always the case. One simple way to help remember the difference is that a. One implication is that a. Equals b will nearly always return some value for a and b , regardless of type the normal way to overload is to just return false if b is an unkown type.

For strings you want to be careful of culture specific comparisons. The classic example is the german double S, that looks a bit like a b. For string comparisons that are culture sensitive use: String. Compare expected, value, StringComparison Equals are equivalent apart from the possibility of calling. Equals on a null instance which would give you a NullReferenceException. Returns: a lexicographic-order comparator composed of this and then the other comparator Throws: NullPointerException - if the argument is null.

Implementation Requirements: This default implementation behaves as if thenComparing comparing keyExtractor, cmp. Type Parameters: U - the type of the sort key Parameters: keyExtractor - the function used to extract the sort key keyComparator - the Comparator used to compare the sort key Returns: a lexicographic-order comparator composed of this comparator and then comparing on the key extracted by the keyExtractor function Throws: NullPointerException - if either argument is null.

Implementation Requirements: This default implementation behaves as if thenComparing comparing keyExtractor. Type Parameters: U - the type of the Comparable sort key Parameters: keyExtractor - the function used to extract the Comparable sort key Returns: a lexicographic-order comparator composed of this and then the Comparable sort key. Throws: NullPointerException - if the argument is null.

Implementation Requirements: This default implementation behaves as if thenComparing comparingInt keyExtractor.

Parameters: keyExtractor - the function used to extract the integer sort key Returns: a lexicographic-order comparator composed of this and then the int sort key Throws: NullPointerException - if the argument is null.

Implementation Requirements: This default implementation behaves as if thenComparing comparingLong keyExtractor. Parameters: keyExtractor - the function used to extract the long sort key Returns: a lexicographic-order comparator composed of this and then the long sort key Throws: NullPointerException - if the argument is null. Implementation Requirements: This default implementation behaves as if thenComparing comparingDouble keyExtractor.

Parameters: keyExtractor - the function used to extract the double sort key Returns: a lexicographic-order comparator composed of this and then the double sort key Throws: NullPointerException - if the argument is null. The returned comparator is serializable and throws NullPointerException when comparing null. Type Parameters: T - the Comparable type of element to be compared Returns: a comparator that imposes the reverse of the natural ordering on Comparable objects.

Type Parameters: T - the Comparable type of element to be compared Returns: a comparator that imposes the natural ordering on Comparable objects. When both are null , they are considered equal.

If both are non-null, the specified Comparator is used to determine the order. If the specified comparator is null , then the returned comparator considers all non-null values to be equal.

The returned comparator is serializable if the specified comparator is serializable. Equals method with the following signature:. For more information, see the Relational and type-testing operators section of the C language specification.

For more information about equality of record types, see the Equality members section of the records feature proposal note. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info.

Contents Exit focus mode.