Check if a value exists in ArrayList

Question

How can I check if a value that is written in scanner exists in an ArrayList   List lt CurrentAccount gt  lista   new ArrayList lt CurrentAccount gt      CurrentAccount conta1   new CurrentAccount  Alberto Carlos   1052   CurrentAccount conta2   new CurrentAccount  Pedro Fonseca   30   CurrentAccount conta3   new CurrentAccount  Ricardo Vitor   1534   CurrentAccount conta4   new CurrentAccount  Jo  o Lopes   3135    lista add conta1   lista add conta2   lista add conta3   lista add conta4    Collections sort lista    System out printf  Bank Accounts       n    Iterator lt CurrentAccount gt  itr   lista iterator    while  itr hasNext          CurrentAccount element   itr next        System out printf element           n      System out println

User · Answer

We can use contains method to check if an item exists if we have provided the implementation of equals and hashCode else object reference will be used for equality comparison  Also in case of a list contains is O n  operation where as it is O 1  for HashSet so better to use later  In Java 8 we can use streams also to check item based on its equality or based on a specific property   Java 8  CurrentAccount conta5   new CurrentAccount  Jo  o Lopes   3135   boolean itemExists   lista stream   anyMatch c - gt  c equals conta5      provided equals and hashcode overridden System out println itemExists      true  String nameToMatch    Ricardo Vitor   boolean itemExistsBasedOnProp   lista stream   map CurrentAccount  getName  anyMatch nameToMatch  equals   System out println itemExistsBasedOnProp     true

User · Answer

Just use ArrayList contains desiredElement    For example  if you re looking for the conta1 account from your example  you could use something like   if  lista contains conta1         System out println  Account found      else       System out println  Account not found        Edit  Note that in order for this to work  you will need to properly override the equals   and hashCode   methods  If you are using Eclipse IDE  then you can have these methods generated by first opening the source file for your CurrentAccount object and the selecting Source  gt  Generate hashCode   and equals

User · Answer

Just use  contains   For example  if you were checking if an ArrayList arr contains a value val  you would simply run arr contains val   which would return a boolean representing if the value is contained   For more information  see the docs for  contains

User · Answer

Please refer to my answer on this post   There is no need to iterate over the List just overwrite the equals method   Use equals instead of         Override public boolean equals  Object object        boolean result   false      if  object    null    object getClass      getClass              result   false        else           EmployeeModel employee    EmployeeModel  object          if  this name equals employee getName     amp  amp  this designation equals employee getDesignation       amp  amp  this age    employee getAge                  result   true                      return result      Call it like this   public static void main String args           EmployeeModel first   new EmployeeModel  Sameer    Developer   25       EmployeeModel second   new EmployeeModel  Jon    Manager   30       EmployeeModel third   new EmployeeModel  Priyanka    Tester   24        List lt EmployeeModel gt  employeeList   new ArrayList lt EmployeeModel gt         employeeList add first       employeeList add second       employeeList add third        EmployeeModel checkUserOne   new EmployeeModel  Sameer    Developer   25       System out println  Check checkUserOne is in list or not        System out println  Is checkUserOne Preasent         employeeList contains checkUserOne         EmployeeModel checkUserTwo   new EmployeeModel  Tim    Tester   24       System out println  Check checkUserTwo is in list or not        System out println  Is checkUserTwo Preasent         employeeList contains checkUserTwo

User · Answer

Better to use a HashSet than an ArrayList when you are checking for existence of a value  Java docs for HashSet says   This class offers constant time performance for the basic operations  add  remove  contains and size    ArrayList contains   might have to iterate the whole list to find the instance you are looking for

User · Answer

public static void linktest         System setProperty  webdriver chrome driver   C   Users  WDSI  Downloads chromedriver exe        driver new ChromeDriver        driver manage   window   maximize        driver get  http   toolsqa wpengine com           List lt WebElement gt  allLinkElements  List lt WebElement gt   driver findElement By xpath    a           int linkcount allLinkElements size          System out println linkcount       List lt WebElement gt  link   driver findElements By tagName  a         String data  HOME       int linkcount link size        System out println linkcount       for int i 0 i lt link size   i               if link get i  getText   contains data                 System out println  true

User · Answer

When Array List contains object of Primitive DataType   Use this function  arrayList contains value    if list contains that value then it will return true else false    When Array List contains object of UserDefined DataType   Follow this below Link    How to compare Objects attributes in an ArrayList   I hope this solution will help you  Thanks

[java] Check if a value exists in ArrayList

Java 8

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