Using ‘==’ instead of .equals for Java strings [duplicate]

by

This is because you’re lucky. The == operator in Java checks for reference equality: it returns true if the pointers are the same. It does not check for contents equality. Identical strings found at compile-time are collapsed into a single String instance, so it works with String literals, but not with strings generated at runtime.

For instance, "Foo" == "Foo" might work, but "Foo" == new String("Foo") won’t, because new String("Foo") creates a new String instance, and breaks any possible pointer equality.

More importantly, most Strings you deal with in a real-world program are runtime-generated. User input in text boxes is runtime-generated. Messages received through a socket are runtime-generated. Stuff read from a file is runtime-generated. So it’s very important that you use the equals method, and not the == operator, if you want to check for contents equality.

More Related Contents:

  1. Why 2 return statements are mandatory in equals method
  2. What issues should be considered when overriding equals and hashCode in Java?
  3. Why do I need to override the equals and hashCode methods in Java?
  4. Compare two objects with .equals() and == operator
  5. What’s the difference between “.equals” and “==”? [duplicate]
  6. Overriding the java equals() method – not working?
  7. Any reason to prefer getClass() over instanceof when generating .equals()?
  8. How to override equals method in Java
  9. why equals() method when we have == operator? [duplicate]
  10. What makes reference comparison (==) work for some strings in Java?
  11. Getting an element from a Set
  12. How to check if my string is equal to null?
  13. Using == operator in Java to compare wrapper objects
  14. Is there a Java utility to do a deep comparison of two objects? [closed]
  15. compareTo() vs. equals()
  16. Why do we have to override the equals() method in Java?
  17. comparing arrays in java
  18. Apache Commons equals/hashCode builder [closed]
  19. Hashcode and Equals for Hashset [duplicate]
  20. what is the difference between == operator and equals()? (with hashcode() ???)
  21. Java – equals method in base class and in subclasses
  22. What does comparison being consistent with equals mean ? What can possibly happen if my class doesn’t follow this principle?
  23. How to implement hashCode and equals method
  24. Is it possible in java make something like Comparator but for implementing custom equals() and hashCode()
  25. Why can’t we use ‘==’ to compare two float or double numbers [duplicate]
  26. Is there a way to check if two Collections contain the same elements, independent of order?
  27. Why are two AtomicIntegers never equal?
  28. Why are these == but not `equals()`?
  29. String equals and == with String concatenation [duplicate]
  30. Demonstrating string comparison with Java

Leave a Comment