Metoden contains() för List-gränssnittet i Java används för att kontrollera om det angivna elementet finns i den givna listan eller inte.
Syntax:
public boolean contains(Object obj) object-element to be searched for>
Parametrar: Denna metod accepterar en enda parameter obj vars närvaro i denna lista ska testas.
stack java
Returvärde: Det returnerar sant om det angivna elementet finns i listan annars returnerar det falskt.
Nedanstående program illustrerar metoden contains() i List:
Program 1: Demonstrera hur metoden contains() fungerar i List of heltal.
// Java code to demonstrate the working of> // contains() method in List interface> > import> java.util.*;> > class> GFG {> >public> static> void> main(String[] args)> >{> >// creating an Empty Integer List> >List arr =>new> ArrayList(>4>);> > >// using add() to initialize values> >// [1, 2, 3, 4]> >arr.add(>1>);> >arr.add(>2>);> >arr.add(>3>);> >arr.add(>4>);> > >// use contains() to check if the element> >// 2 exits or not> >boolean> ans = arr.contains(>2>);> > >if> (ans)> >System.out.println(>'The list contains 2'>);> >else> >System.out.println(>'The list does not contains 2'>);> > >// use contains() to check if the element> >// 5 exits or not> >ans = arr.contains(>5>);> > >if> (ans)> >System.out.println(>'The list contains 5'>);> >else> >System.out.println(>'The list does not contains 5'>);> >}> }> |
>
>Produktion:
The list contains 2 The list does not contains 5>
Program 2: Demonstrera hur metoden contains() fungerar i List of string.
javatpoint java
för string array java
// Java code to demonstrate the working of> // contains() method in List of string> > import> java.util.*;> > class> GFG {> >public> static> void> main(String[] args)> >{> >// creating an Empty String List> >List arr =>new> ArrayList(>4>);> > >// using add() to initialize values> >// ['geeks', 'for', 'geeks']> >arr.add(>'geeks'>);> >arr.add(>'for'>);> >arr.add(>'geeks'>);> > >// use contains() to check if the element> >// 'geeks' exits or not> >boolean> ans = arr.contains(>'geeks'>);> > >if> (ans)> >System.out.println(>'The list contains geeks'>);> >else> >System.out.println(>'The list does not contains geeks'>);> > >// use contains() to check if the element> >// 'coding' exits or not> >ans = arr.contains(>'coding'>);> > >if> (ans)> >System.out.println(>'The list contains coding'>);> >else> >System.out.println(>'The list does not contains coding'>);> >}> }> |
>
>Produktion:
The list contains geeks The list does not contains coding>
Praktisk applikation: I sökoperationer kan vi kontrollera om ett givet element finns i en lista eller inte.
Referens: https://docs.oracle.com/javase/7/docs/api/java/util/List.html#contains(java.lang.Object)