Best way to format multiple or conditions in an if statement Java

Question

A simple question but Google hasn t been helping much   I have an if statement with many conditions  have to check for 10 or 15 constants to see if any of them are present    Instead of writing something like   if  x    12    x    16    x    19           is there any way to format it like  if x is  12  16  19     Just wondering if there is an easier way to code this  any help appreciated   Edit   The answers have been very helpful  but I was asked to add more detail by a few people so I will do that to satiate their curiosity   I was making a date validation class that needed to make sure days were not   30 in the months that have only 30 days  of which there are 4  I think  and I was writing an if statement to check things like this   if  day  gt  30  amp  amp   month    4    month    6    month    9    month    11     I was just wondering if there was a faster way to code things like that - many of the answers below have helped

User · Accepted Answer

I use this kind of pattern often  It s very compact      Define a constant in your class  Use a HashSet for performance private static final Set lt Integer gt  values   new HashSet lt Integer gt  Arrays asList 12  16  19        In your method  if  values contains x                 A HashSet is used here to give good look-up performance - even very large hash sets are able to execute contains   extremely quickly   If performance is not important  you can code the gist of it into one line   if  Arrays asList 12  16  19  contains x     but know that it will create a new ArrayList every time it executes

User · Answer

If the set of possibilities is  compact   i e  largest-value - smallest-value is  say  less than 200  you might consider a lookup table   This would be especially useful if you had a structure like   if  x    12    x    16    x    19         else if  x  34    x    55         else if         Set up an array with values identifying the branch to be taken  1  2  3 in the example above  and then your tests become  switch dispatchTable x         case 1                      break      case 2                      break      case 3                      break      Whether or not this is appropriate depends on the semantics of the problem   If an array isn t appropriate  you could use a Map lt Integer Integer gt   or if you just want to test membership for a single statement  a Set lt Integer gt  would do   That s a lot of firepower for a simple if statement  however  so without more context it s kind of hard to guide you in the right direction

User · Answer

No you cannot do that in Java  you can however write a method as follows   boolean isContains int i  int     numbers           code to check if i is one of the numbers     for  int n   numbers            if  i    n  return true            return false

User · Answer

Do you want to switch to this    switch x        case 12      case 16      case 19             Do something         break      default            Do nothing or something else           break

User · Answer

You could look for the presence of a map key or see if it s in a set    Depending on what you re actually doing  though  you might be trying to solve the problem wrong

User · Answer

Use a collection of some sort - this will make the code more readable and hide away all those constants  A simple way would be with a list      Declared with constants private static List lt Integer gt  myConstants   new ArrayList lt Integer gt          add 12       add 16       add 19           Wherever you are checking for presence of the constant if myConstants contains x           ETC     As Bohemian points out the list of constants can be static so it s accessible in more than one place   For anyone interested  the list in my example is using double brace initialization  Since I ran into it recently I ve found it nice for writing quick  amp  dirty list initializations

User · Answer

With Java 8  you could use a primitive stream   if  IntStream of 12  16  19  anyMatch i - gt  i    x     but this may have a slight overhead  or not   depending on the number of comparisons

[java] Best way to format multiple 'or' conditions in an if statement (Java)

Examples related to java

Examples related to syntax

Examples related to if-statement