Metode Java ArrayList addAll().

Yen sampeyan perlu kanggo nambah kabeh unsur siji ArrayList () koleksi liyane, sampeyan bisa nggunakake addAll () cara saka kelas ArrayList Jawa . Ing artikel iki, aku bakal nerangake cara kerjane lan menehi sawetara conto kode.

ArrayList addAll() method signature

Ana rong varian cara java.util.ArrayList.addAll . Kene lagi.

boolean addAll(Collection<? extends E> c)

Cara iki bali bener yen dhaftar diganti minangka asil saka telpon, nanging sing paling Jahwéh, iku nambah kabeh unsur koleksi kasebut menyang mburi dhaftar iki, supaya padha bali dening Iterator koleksi kasebut. Elemen c minangka dhaptar sing bakal ditambahake menyang ArrayList . Uga cara mbalang NullPointerException yen koleksi kasebut null.

boolean addAll(int index, Collection<? extends E> c)

Cara iki nglebokake kabeh unsur ing koleksi kasebut c menyang dhaptar iki, wiwit saka indeks posisi sing ditemtokake.

ArrayList addAll() conto sintaks

Iki minangka telpon menyang metode ArrayList addAll () ing program Java:

myList.addAll(myNewList)) 

Ngendi myList minangka ArrayList asli lan myNewList minangka dhaptar, kabeh nilai sing bakal ditambahake ing myList yen ana.

myList.addAll(2, myNewList)) 

A varian saka ArrayList addAll () cara karo loro paramèter. Kabeh unsur saka myNewList bakal ditambahake menyang myList , lan unsur pisanan myNewList[0] bakal dadi myList[2] , myNewList[1] saiki dadi myList[3] , lan sateruse. Unsur saka dhaptar asli, wiwit saka nomer 2, digawa menyang buntut saka dhaftar combo anyar.

ArrayList addAll() conto kode

Saiki wektu kanggo sawetara conto kode. Ayo nggawe dhaptar kanca-kanca, lan nelpon 'kanca', lan nambah jeneng ing kono. Ngomong, kita miwiti kuliah lan nggawe sawetara kanca anyar bebarengan. Wektu sing apik kanggo nggawe dhaptar kanca anyar kanggo dheweke. Wektu liwati, sampeyan nggawe manawa kanca anyar sampeyan nyata, mula sampeyan mutusake pindhah menyang dhaptar kanca utama. Sampeyan bisa nindakake iku nggunakake addAll () cara. Ing program, kita bakal print kanggo console dhaftar dhisikan saka kanca, dhaftar kanca anyar, dhaftar dianyari kanca, uga Nilai boolean bali dening addAll () cara . Ngasilake bener yen dhaptar asli diganti amarga operasi metode kasebut lan salah yen ora kedadeyan.

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

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

           List<String> friends = new ArrayList<>();
           friends.add("Johnny");
           friends.add("Ivy");
           friends.add("Rick");
           System.out.println(friends);
           List<String> newFriends = new ArrayList<>();
           newFriends.add("Andrew");
           newFriends.add("Alex");
           newFriends.add("Neil");
           System.out.println(newFriends);
           //let's print out the value addAll() method returns
           //here it's true because list friends was changed
           System.out.println(friends.addAll(newFriends));
           System.out.println("My new list with new friends added: ");
           System.out.println(friends);
       }
   }

output yaiku: Yen kita nindakake operasi sing padha nanging nyoba nambah dhaptar kosong menyang kanca, cara kasebut bakal bisa digunakake, nanging bakal bali palsu, ora bener amarga dhaptar asli ora diganti.

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

public class AddAllDemo3 {
   public static void main(String[] args) {
       List<String> friends = new ArrayList<>();
       friends.add("Johnny");
       friends.add("Ivy");
       friends.add("Rick");
       System.out.println(friends);
       List<String> newFriends = new ArrayList<>();
       System.out.println(newFriends);
       System.out.println(friends.addAll(newFriends));
       System.out.println("My new list with new friends added: ");
       System.out.println(friends);
   }
}

Output yaiku: Saiki ayo nyoba metode addAll () kanthi rong paramèter.

boolean addAll(int index, Collection<? extends E> c)

Ayo nambah kanca anyar ing dhaptar maneh, ora ing buntut, nanging ing tengah. Ayo ngomong langsung sawise Johnny, sing ing kasus kita minangka unsur nomer nol.

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

public class AddAllDemo2 {
   public static void main(String[] args) {

       List<String> friends = new ArrayList<>();
       friends.add("Johnny");
       friends.add("Ivy");
       friends.add("Rick");
       System.out.println(friends);
       List<String> newFriends = new ArrayList<>();
       newFriends.add("Andrew");
       newFriends.add("Alex");
       newFriends.add("Neil");
       System.out.println(newFriends);
       System.out.println(friends.addAll(1, newFriends));
       System.out.println("My new list with new friends added: ");
       System.out.println(friends);
   }
}

Hasil sing dikarepake saka program kasebut: Andrew saiki dadi nomer 1 ing dhaptar gabungan, Alex - 2, Neil - 3, lan Ivy, sing dadi # 1 sadurunge, wis pindhah menyang posisi 4.