Is using java Map.containsKey() redundant when using map.get()

by

Some Map implementations are allowed to have null values, eg HashMap, in this case if get(key) returns null it does not guarantee that there is no entry in the map associated with this key.

So if you want to know if a map contains a key use Map.containsKey. If you simply need a value mapped to a key use Map.get(key). If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; In such case Map.containsKey is useless and will affect performance. Moreover, in case of concurrent access to a map (eg ConcurrentHashMap), after you tested Map.containsKey(key) there is a chance that the entry will be removed by another thread before you call Map.get(key).

More Related Contents:

  1. Why is printing “B” dramatically slower than printing “#”?
  2. Difference between declaring variables before or in loop?
  3. How can I initialise a static Map?
  4. Does use of final keyword in Java improve the performance?
  5. Why is creating a Thread said to be expensive?
  6. Is there a performance difference between a for loop and a for-each loop?
  7. .toArray(new MyClass[0]) or .toArray(new MyClass[myList.size()])?
  8. Swing animation running extremely slow
  9. Java lambdas 20 times slower than anonymous classes
  10. Case insensitive string as HashMap key
  11. System.currentTimeMillis() vs. new Date() vs. Calendar.getInstance().getTime()
  12. Faster alternatives to Java’s reflection [closed]
  13. Java: what’s the big-O time of declaring an array of size n?
  14. Calling getters on an object vs. storing it as a local variable (memory footprint, performance)
  15. Performance difference between Java 8 lambdas and anonymous inner classes
  16. Best practice for passing many arguments to method?
  17. How do I use the new computeIfAbsent function?
  18. What is the time complexity of HashMap.containsKey() in java?
  19. Most efficient Java primitive collections library [closed]
  20. Know of any Java garbage collection log analysis tools? [closed]
  21. What is the fastest Java collection with the basic functionality of a Queue?
  22. Strange branching performance
  23. What is the quantitative overhead of making a JNI call?
  24. Java split String performances
  25. Is it possible to force an existing Java application to use no more than x cores?
  26. ArrayList vs. Vectors in Java if thread safety isn’t a concern
  27. How to check whether given string is a word
  28. Most elegant way to join a Map to a String in Java 8
  29. Performance of WebView in JavaFX
  30. What GC parameters is a JVM running with?

Leave a Comment