Java int to String - Integer toString i vs new Integer i toString

Question

Sometimes java puzzles me  I have a huge amount of int initializations to make   What s the real difference    Integer toString i  new Integer i  toString

User · Answer

Better   Integer valueOf i  toString

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In terms of performance measurement  if you are considering the time performance then the Integer toString i   is expensive if you are calling less than 100 million times  Else if it is more than 100 million calls then the new Integer 10  toString   will perform better   Below is the code through u can try to measure the performance   public static void main String args                  int MAX ITERATION   10000000          long starttime   System currentTimeMillis            for  int i   0  i  lt  MAX ITERATION    i                String s   Integer toString 10                     long endtime   System currentTimeMillis            System out println  diff1       endtime-starttime             starttime   System currentTimeMillis            for  int i   0  i  lt  MAX ITERATION    i                String s1   new Integer 10  toString                      endtime   System currentTimeMillis            System out println  diff2       endtime-starttime            In terms of memory  the      new Integer i  toString      will take more memory as it will create the object each time  so memory fragmentation will happen

User · Answer

Integer toString calls the static method in the class Integer  It does not need an instance of Integer   If you call new Integer i  you create an instance of type Integer  which is a full Java object encapsulating the value of your int  Then you call the toString method on it to ask it to return a string representation of itself   If all you want is to print an int  you d use the first one because it s lighter  faster and doesn t use extra memory  aside from the returned string      If you want an object representing an integer value   to put it inside a collection for example   you d use the second one  since it gives you a full-fledged object to do all sort of things that you cannot do with a bare int

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new Integer i  toString    This statement creates the object of the Integer and then call its methods toString i  to return the String representation of Integer s value   Integer toString i   It returns the String object representing the specific int  integer   but here toString int  is a static method    Summary is in first case it returns the objects string representation  where as in second case it returns the string representation of integer

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I also highly recommend using  int integer   42  String string   integer         Simple and effective

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Although I like fhucho s recommendation of   String valueOf i    The irony is that this method actually calls   Integer toString i    Thus  use String valueOf i  if you like how it reads and you don t need radix  but also knowing that it is less efficient than Integer toString i

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Another option is the static String valueOf method   String valueOf i    It feels slightly more right than Integer toString i  to me  When the type of i changes  for example from int to double  the code will stay correct

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Here  Integer toString calls the static method in the class Integer  It does not require the object to call   If you call new Integer i  you first create an instance of type Integer  which is a full Java object encapsulating the value of your int i  Then you call the toString method on it to ask it to return a string representation of itself

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1 Integer toString i   Integer i   new Integer 8          returns a string representation of the specified integer with radix 8  String retval   i toString 516  8   System out println  Value       retval     2 new Integer i  toString      int i   506   String str   new Integer i  toString    System out println str           new Integer i  toString   getClass        506   class java lang String

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new Integer i  toString   first creates a  redundant  wrapper object around i  which itself may be a wrapper object Integer    Integer toString i  is preferred because it doesn t create any unnecessary objects

User · Answer

Simple way is just concatenate    with integer   int i   100   String s        i    now s will have 100 as string value

[java] Java int to String - Integer.toString(i) vs new Integer(i).toString()

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