Metode ArrayList removeAll() ing Jawa

Cara ArrayList removeAll() ing Jawa ora mbusak kabeh unsur saka ArrayList sing tepat , amarga jenenge. Yen sampeyan mbutuhake operasi iki, gunakake metode ArrayList clear () . Boten kados cetha () , mbusak cara removeAll () kabeh item saka dhaftar tartamtu sing ana ing koleksi liyane.

removeAll () sintaks lan deklarasi

Mangkene sintaks metode:

boolean removeAll(Collection<?> c)

Where c koleksi sing ngemot unsur kanggo dibusak saka dhaftar iki. Cara iki bali bener yen dhaptar iki diganti minangka asil saka telpon. Uga bisa mbuwang pangecualian: ClassCastException - yen kelas saka unsur dhaptar iki ora kompatibel karo koleksi kasebut NullPointerException - yen dhaptar ngemot unsur null lan koleksi kasebut ora ngidini unsur null, utawa yen koleksi kasebut null

conto kode removeAll ().

Contone, sampeyan duwe dhaptar kanca ing jaringan sosial. Lha saiki wis biasa. Uga, ayo ngomong yen sampeyan wong sing tliti, lan ketik kabeh wong sing nandhang lara ing dhaptar mungsuh khusus, preduli manawa mungsuh sampeyan ana ing antarane kanca jaringan sosial utawa ora. Sampeyan wis mutusake mbusak dhaptar kanca saka kabeh wong sing ora seneng. Cara removeAll () mesthi bakal mbantu:

import java.util.ArrayList;
import java.util.List;

public class RemoveAll2Example {
  
       public static void main(String[] args) {

           
           List<String> friendList = new ArrayList<String>();

           // use add() method to add friends into your friend list
           friendList.add("Alex");
           friendList.add("Ivy");
           friendList.add("Victor");
           friendList.add("Peter");
           friendList.add("Lenny");
           friendList.add("Olly");
           friendList.add("Stu");
           friendList.add("Scott");
           friendList.add("Olivia");

           System.out.println("My old friend list: "+ friendList);

           //create and add elements to foe list 
           List<String> foeList = new ArrayList<String>();

           foeList.add("Ben");
           foeList.add("Scott");
           foeList.add("Chuck");
           foeList.add("Olly");
           foeList.add("Sam");
           System.out.println("All my enemies: "+ foeList);

           //remove all foeList elements from friendList list if they exist
           friendList.removeAll(foeList);
           System.out.println("new friend List without foes: "+ friendList);
       }
   }

Output yaiku: Nalika sampeyan bisa ndeleng, cara mbusak mungsuh Olly lan Scott. Sampeyan ora duwe musuh Ben, Chuck lan Sam ing dhaptar kanca. Sampeyan mbokmenawa wis ngeweruhi sing miturut deklarasi cara removeAll () sampeyan bisa mbusak saka dhaftar ora mung nilai saka dhaftar liyane, nanging saka koleksi acak. Ayo duwe conto karo HashMap . Ing kasus iki, sampeyan kudu tegas nuduhake yen sampeyan pengin mbusak cathetan sing cocog, contone, karo nilai (removeAll (collection.values ​​()) utawa tombol (removeAll (collection.keySet ()) . Ayo mbayangno sing kita duwe HashMap kanthi jeneng kabeh bocah-bocah wadon ing antarane kanca-kanca, lan kita kudu ninggalake mung lanang ing friendList(Aku ora ngerti kenapa iki bisa uga dibutuhake, nanging sampeyan ora ngerti). Ayo bali menyang conto karo dhaptar kanca lawas, nggawe HasMap bocah-bocah wadon lan mbusak saka dhaptar kanca kabeh bocah wadon sing jenenge ditulis ing nilai HashMap kita .

import java.util.*;

public class RemoveAll2Example {
  
       public static void main(String[] args) {

          // create an empty array list and full it up using Java 9 Factory Methods  in one line
List<String> friendList= new ArrayList<>(List.of("Alex", "Ivy", "Victor", "Peter", "Lenny", "Olly", "Stu", "Scott", "Olivia"));

           System.out.println("My old friend list: "+ friendList);

           // Creating hashMap with girls keys and names also using using Java 9 Factory Methods   
           Map<Integer, String> girls = new HashMap<>(Map.of(1, "Olly", 2, "Olivia", 3, "Loe", 4, "Ivy"));
           friendList.removeAll(girls.values());
           System.out.println("boys only friendList: " + friendList);
       }
   }

Punika output:

Sawetara kasus khusus

Ing awal artikel iki aku wrote sing kanggo mbusak kabeh nilai saka dhaftar, sampeyan kudu nggunakake cara ArrayList cetha () . Iku, nanging mesthi sampeyan uga bisa nggunakake cara removeAll () iki. Sampeyan mbokmenawa wis ngira carane nindakake iki:

myList.RemoveAll (myList);

Ayo menehi conto. Ing pas karo sosiopati, ayo kosongake kabeh friendList:

 import java.util.*;

public class RemoveAll2Example {
  
       public static void main(String[] args) {

           // create an empty array list and full it up using  Java 9 Factory Methods  in one line
           List<String> friendList= new ArrayList<>(List.of("Alex", "Ivy", "Victor", "Peter", "Lenny", "Olly", "Stu", "Scott", "Olivia"));
           System.out.println("My old friend list: "+ friendList);

           friendList.removeAll(friendList);
           System.out.println("my new empty friendlist...:" + friendList);
       }
   }

Punika output: Paling ora, ayo nyoba mbusak unsur koleksi null saka ArrayList :

import java.util.*;

public class RemoveAll2Example {
  
       public static void main(String[] args) {

           List<String> friendList = new ArrayList<>(List.of("Alex", "Ivy", "Victor", "Peter", "Lenny", "Olly", "Stu", "Scott", "Olivia"));
           System.out.println("My old friend list: "+ friendList);

           // we are happy not to have foes 
           List<String> foeList = null;
          
           //trying to remove all foeList elements from friendList list 
            friendList.removeAll(foeList);
            System.out.println("my new friendlist:" + friendList);
       }
   }

Miturut definisi metode removeAll () kita duwe pangecualian ing output: