Searching in a ArrayList with custom objects for certain strings

Question

I have a ArrayList with custom objects  I want to search inside this ArrayList for Strings   The class for the objects look like this   public class Datapoint implements Serializable      private String stateBased    private String name    private String priority    private String mainNumber    private String groupadress    private String dptID     public Datapoint           public String getMainNumber         return mainNumber         public void setMainNumber String mainNumber        this mainNumber   mainNumber         public String getName         return name           and so on   I know how to search for a string in a ArrayList but how to do that in a ArrayList with my custom objects   ArrayList lt String gt  searchList   new ArrayList lt String gt     String search    a   int searchListLength   searchList size    for  int i   0  i  lt  searchListLength  i      if  searchList get i  contains search       Do whatever you want here       So I want to have a function to search in my ArrayList with for example five objects for all  name  strings

User · Accepted Answer

The easy way is to make a for where you verify if the atrrtibute name of the custom object have the desired string      for Datapoint d   dataPointList           if d getName      null  amp  amp  d getName   contains search                something here         I think this helps you

User · Answer

Probably something like   ArrayList lt DataPoint gt  myList   new ArrayList lt DataPoint gt       Fill up myList with your Data Points    Traversal for DataPoint myPoint   myList        if myPoint getName      null  amp  amp  myPoint getName   equals  Michael Hoffmann                Process data do whatever you want         System out println  Found it

User · Answer

For a custom class to work properly in collections you ll have to implement override the equals   methods of the class  For sorting also override compareTo     See this article or google about how to implement those methods properly

User · Answer

boolean found   for CustomObject obj   ArrayOfCustObj        if obj getName equals  Android             found   true

User · Answer

UPDATE  Using Java 8 Syntax  List lt DataPoint gt  myList   new ArrayList lt  gt       Fill up myList with your Data Points  List lt DataPoint gt  dataPointsCalledJohn        myList      stream        filter p- gt  p getName   equals   john          collect Collectors toList       If you don t mind using an external libaray - you can use Predicates from the Google Guava library as follows   class DataPoint       String name       String getName     return name       Predicate lt DataPoint gt  nameEqualsTo final String name        return new Predicate lt DataPoint gt               public boolean apply DataPoint dataPoint                return dataPoint getName   equals name                       public void main String   args  throws Exception        List lt DataPoint gt  myList   new ArrayList lt DataPoint gt           Fill up myList with your Data Points      Collection lt DataPoint gt  dataPointsCalledJohn               Collections2 filter myList  nameEqualsTo  john

User · Answer

Use Apache CollectionUtils   CollectionUtils find myList  new Predicate        public boolean evaluate Object o          return name equals   MyClass  o  getName

User · Answer

contains   method just calls equals   on ArrayList elements  so you can overload your class s equals   based on the name class variable  Return true from equals   if name is equal to the matching String  Hope this helps

User · Answer

try this   ArrayList lt Datapoint  gt  searchList   new ArrayList lt Datapoint  gt     String search    a   int searchListLength   searchList size    for  int i   0  i  lt  searchListLength  i      if  searchList get i  getName   contains search       Do whatever you want here

User · Answer

String string  for  Datapoint d   dataPointList           Field   fields   d getFields       for  Field f   fields          String value    String  g get d         if  value equals string                Do your stuff

[java] Searching in a ArrayList with custom objects for certain strings

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