7

Which is the best one to choose to store list of string on the basis of performance.

Which one offers the best performance.

Thanks.

Kathir
  • 2,733
  • 12
  • 39
  • 67
  • performance wise arrays are good. But list gives you advance features which array can not provide. – AJ. Dec 11 '13 at 06:40
  • Define "performance". Space, speed, reliability? How many Strings are we talking about? – user949300 Dec 11 '13 at 06:40
  • You can check this link http://stackoverflow.com/questions/13639712/what-efficient-java-collection-would-be-used-to-store-a-million-strings – Abdul Salam Dec 11 '13 at 06:41
  • 2
    -1, A StringBuilder is s different data sbructure (and used for different purposes) compared to an Array or List. And as has already been mentioned you haven't defined what performance means to you so the question can't be answered. – camickr Dec 11 '13 at 06:45

5 Answers5

12

ArrayList is a good general purpose List and will usually out-perform an Array or LinkedList. Here is the breakdown in terms of time complexity (V is the type, i is an index):

       Type | add(V) | remove(V) | get(i) | 
-------------------------------------------
      Array |  O(n)  |    O(n)   |  O(1)  |
  ArrayList |  O(1)  |    O(n)   |  O(1)  |
 LinkedList |  O(1)  |    O(1)   |  O(n)  |

In general you can use this rule:

Array: Use if you know the exact number of elements and don't need to add or remove elements.

List: Use if you don't know the exact number of elements and need to add or remove elements.

StringBuilder is completly different. StringBuilder is a mutable String. You can think of it as List<Character>. In that sense, it is probably not what you need so to compare it to List<String> or String[] is probably not benificial.

bcorso
  • 45,608
  • 10
  • 63
  • 75
2

List of String literals before java 7 will just consume your permgen Area which may led to JVM crash. So if you have too many String better go for Stringbuilder. Stringbuilder internally uses char array. However using Stringbuilder for storing list of String you may have to use special character for separation and then split() to retrieve back your list.

Better alternative would be to go for an String array. As mentioned earlier even Stringbuilder uses an char array. So if you are sure you want to store list of String this would be good option. But if this is the only goal I would say why not use ArratList... you don't have to bother about the size of the array.

Aniket Thakur
  • 66,731
  • 38
  • 279
  • 289
  • 1
    How would you access individual Strings in a StringBuilder? A StringBuilder is s different data sbructure compared to and Array or List. – camickr Dec 11 '13 at 06:43
  • Well one way would be to append all String with special character and to get the List you can do something like sbuilder.toString().split(SpChar). You will get arrays of String. – Aniket Thakur Dec 11 '13 at 07:04
  • So now you have to parse the data to access it and then you would have the data stored in two places, once in the StringBuilder and once in the Array. Doesn't seem very efficient to me from a performance point of view. – camickr Dec 11 '13 at 07:10
  • Agreed it is better to use String array. Infact as I specified Stringbuilder uses char array as it internal DS. – Aniket Thakur Dec 11 '13 at 07:15
1

Always use StringBuilder when constructing large strings. Although the speed difference is not noticeable, this is the most efficient.

I've also heard somewhere that Java uses a builder internally when you use the plus operator on strings. Although I'm uncertain, it is highly unlikely.

Georgian
  • 8,795
  • 8
  • 46
  • 87
  • 1
    Java Compiler does replace concatenated strings with a `new StringBuilder().append(first).append(second)...` construct (or `StringBuffer`?). You can see it first hand when you decompile a class with string concatenation. – Cebence Dec 11 '13 at 07:58
  • @Cebence Hmm, so how does it decide whether to use buffer or builder? – Georgian Dec 11 '13 at 09:37
  • `StringBuffer?` meant maybe it's that one, I am not sure which one. It might depend on the compiler, but it always uses the same one. – Cebence Dec 11 '13 at 16:33
1

String is an immutable class, it can't be changed. StringBuilder is a mutable class that can be appended to, characters replaced or removed and ultimately converted to a String.

Note that if you are using Java 5 or newer, you should use StringBuilder instead of StringBuffer. From the API documentation:

As of release JDK 5, this class has been supplemented with an equivalent class designed for use by a single thread, StringBuilder. The StringBuilder class should generally be used in preference to this one, as it supports all of the same operations but it is faster, as it performs no synchronization.

For More

Rakesh KR
  • 6,357
  • 5
  • 40
  • 55
0
  • String array can use when you are going to specified size of data. String array is not growable.
  • Collection classes is used when your data is growable. It means that if your array size will vary dynamically or runtime, at that time you can use it.
  • StringBuilder is not used to storing list of data.It appends string data like String buffer. If you search the difference between String VS StringBuffer Vs String Builder, you can get idea
Murali
  • 341
  • 2
  • 7
  • 24