Better way to find index of item in ArrayList

Question

For an Android app  I have the following functionality  private ArrayList lt String gt   categories     eg   horses   camels   etc    private int getCategoryPos String category        for int i   0  i  lt  this  categories size      i            if this  categories get i     category  return i             return -1      Is that the  best  way to write a function for getting an element s position  Or is there a fancy shmancy native function in java the I should leverage

User · Answer

Java API specifies two methods you could use  indexOf Object obj  and lastIndexOf Object obj   The first one returns the index of the element if found  -1 otherwise  The second one returns the last index  that would be like searching the list backwards

User · Answer

ArrayList has a indexOf   method  Check the API for more  but here s how it works   private ArrayList lt String gt   categories     Initialize all this stuff  private int getCategoryPos String category      return  categories indexOf category       indexOf   will return exactly what your method returns  fast

User · Answer

If your List is sorted and has good random access  as ArrayList does   you should look into Collections binarySearch  Otherwise  you should use List indexOf  as others have pointed out   But your algorithm is sound  fwiw  other than the    others have pointed out

User · Answer

There is indeed a fancy shmancy native function in java you should leverage   ArrayList has an instance method called  indexOf Object o    http   docs oracle com javase 6 docs api java util ArrayList html   You would be able to call it on  categories as follows    categories indexOf  camels    I have no experience with programming for Android - but this would work for a standard Java application   Good luck

User · Answer

the best solution here class Category var Id  Int var Name  String  arrayList is Category list val selectedPositon arrayList map   x- gt x Id   indexOf Category Id  spinner update categories setSelection selectedPositon

User · Answer

Use indexOf   method to find first occurrence of the element in the collection

User · Answer

The best way to find the position of item in the list is by using Collections interface   Eg    List lt Integer gt  sampleList   Arrays asList 10 45 56 35 6 7   Collections binarySearch sampleList  56     Output   2

User · Answer

ArrayList lt String gt  alphabetList   new ArrayList lt String gt     alphabetList add  A       0 index alphabetList add  B       1 index alphabetList add  C       2 index alphabetList add  D       3 index alphabetList add  E       4 index alphabetList add  F       5 index alphabetList add  G       6 index alphabetList add  H       7 index alphabetList add  I       8 index  int position   -1  position   alphabetList indexOf  H    if  position    -1        Log e TAG   Object not found in List      else       Log i TAG       position       Output  List Index   7  If you pass H it will return 7  if you pass J it will return -1 as we defined default value to -1    Done

[java] Better way to find index of item in ArrayList?

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