Integer value comparison

Question

I m a newbie Java coder and I just read a variable of an integer class can be described three different ways in the API   I have the following code    if  count compareTo 0                  System out println out table               count            This is inside a loop and just outputs out table  My goal is to figure out how to see if the value in integer count  gt  0    I realize the count compare 0  is the correct way  or is it count equals 0      I know the count    0 is incorrect  Is this right  Is there a value comparison operator  where its just count 0

User · Answer

You can also use equals    Integer a   0    if  a equals 0             a    0      which is equivalent to    if  a intValue      0            a    0      and also    if  a    0           the Java compiler automatically adds intValue     Note that autoboxing autounboxing can introduce a significant overhead  especially inside loops

User · Answer

It s better to avoid unnecessary autoboxing for 2 reasons    For one thing  it s a bit slower than int  lt  int  as you re  sometimes  creating an extra object   void doSomethingWith Integer integerObject         int i   1000    doSomethingWith i    gets compiled into doSomethingWith Integer valueOf i      The bigger issue is that hidden autoboxing can hide exceptions   void doSomethingWith  Integer count     if  count gt 0      gets compiled into count intValue   gt 0   Calling this method with null will throw a NullPointerException   The split between primitives and wrapper objects in java was always described as a kludge for speed  Autoboxing almost hides this  but not quite - it s cleaner just to keep track of the type  So if you ve got an Integer object  you can just call compare   or intValue    and if you ve got the primitive just check the value directly

User · Answer

Although you could certainly use the compareTo method on an Integer instance  it s not clear when reading the code  so you should probably avoid doing so   Java allows you to use autoboxing  see http   java sun com j2se 1 5 0 docs guide language autoboxing html  to compare directly with an int  so you can do   if  count  gt  0        And the Integer instance count gets automatically converted to an int for the comparison   If you re having trouble understanding this  check out the link above  or imagine it s doing this   if  count intValue    gt  0

User · Answer

Integers are autounboxed  so you can just do   if  count  gt  0

User · Answer

One more thing to watch out for is if the second value was another Integer object instead of a literal  0   the      operator compares the object pointers and will not auto-unbox   ie   Integer a   new Integer 0      Integer b   new Integer 0      int c   0   boolean isSame EqOperator    a  b     false  boolean isSame EqMethod    a equals b      true boolean isSame EqAutoUnbox     a  c   amp  amp   a equals c      also true  because of auto-unbox    Note  for initializing a and b  the Integer constructor     is called explicitly to avoid integer object caching     for the purpose of the example     Calling it explicitly ensures each integer is created     as a separate object as intended     Edited in response to comment by  nolith

User · Answer

well i might be late on this but i would like to share something   Given the input      System out println isGreaterThanZero -1     public static boolean isGreaterThanZero Integer value        return value    null false value compareTo 0   gt  0      Returns false  public static boolean isGreaterThanZero Integer value        return value    null false value intValue    gt  0      Returns true So i think in yourcase  compareTo  will be more accurate

User · Answer

To figure out if an Integer is greater than 0  you can    check if compareTo O  returns a positive number   if  count compareTo 0   gt  0             But that looks pretty silly  doesn t it  Better just    use autoboxing1   if  count  gt  0             This is equivalent to   if  count intValue    gt  0            It is important to note that      is evaluated like this  with the Integer operand unboxed rather than the int operand boxed  Otherwise  count    0 would return false when count was initialized as new Integer 0   because      tests for reference equality     1Technically  the first example uses autoboxing  before Java 1 5 you couldn t pass an int to compareTo  and the second example uses unboxing  The combined feature is often simply called  autoboxing  for short  which is often then extended into calling both types of conversions  autoboxing   I apologize for my lax usage of terminology

[java] Integer value comparison

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