Java - List loop

16300 ワード

リストループ7方式

  • 人はItableだと思いますforeach()utilは毒性を好む.
  • セグメントforEachを使用する場合、閉じた役割ドメインで定義されたローカル変数「変数名」はfinalまたはfinalエラーである必要があります.したがって、クラスセグメントに変数を作成するか、2回使用します.
  • の演技の違いは小さいので、ネストループを重視し、アルゴリズムは効率的です.
  • import java.util.*;
     
    /**
     * @author Crunchify.com
     * How to iterate through Java List? Seven (7) ways to Iterate Through Loop in Java.
     * 1. Simple For loop
     * 2. Enhanced For loop
     * 3. Iterator
     * 4. ListIterator
     * 5. While loop
     * 6. Iterable.forEach() util
     * 7. Stream.forEach() util
     */
     
    public class CrunchifyIterateThroughList {
     
        public static void main(String[] argv) {
     
            // create list
            List<String> crunchifyList = new ArrayList<String>();
     
            // add 4 different values to list
            crunchifyList.add("Facebook");
            crunchifyList.add("Paypal");
            crunchifyList.add("Google");
            crunchifyList.add("Yahoo");
     
            // Other way to define list is - we will not use this list :)
            List<String> crunchifyListNew = Arrays.asList("Facebook", "Paypal", "Google", "Yahoo");
     
            // Simple For loop
            System.out.println("==============> 1. Simple For loop Example.");
            for (int i = 0; i < crunchifyList.size(); i++) {
                System.out.println(crunchifyList.get(i));
            }
     
            // New Enhanced For loop
            System.out.println("\n==============> 2. New Enhanced For loop Example..");
            for (String temp : crunchifyList) {
                System.out.println(temp);
            }
     
            // Iterator - Returns an iterator over the elements in this list in proper sequence.
            System.out.println("\n==============> 3. Iterator Example...");
            Iterator<String> crunchifyIterator = crunchifyList.iterator();
            while (crunchifyIterator.hasNext()) {
                System.out.println(crunchifyIterator.next());
            }
     
            // ListIterator - traverse a list of elements in either forward or backward order
            // An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration,
            // and obtain the iterator's current position in the list.
            System.out.println("\n==============> 4. ListIterator Example...");
            ListIterator<String> crunchifyListIterator = crunchifyList.listIterator();
            while (crunchifyListIterator.hasNext()) {
                System.out.println(crunchifyListIterator.next());
            }
     
            // while loop
            System.out.println("\n==============> 5. While Loop Example....");
            int i = 0;
            while (i < crunchifyList.size()) {
                System.out.println(crunchifyList.get(i));
                i++;
            }
     
            // Iterable.forEach() util: Returns a sequential Stream with this collection as its source
            System.out.println("\n==============> 6. Iterable.forEach() Example....");
            crunchifyList.forEach((temp) -> {
                System.out.println(temp);
            });
     
            // collection Stream.forEach() util: Returns a sequential Stream with this collection as its source
            System.out.println("\n==============> 7. Stream.forEach() Example....");
            crunchifyList.stream().forEach((crunchifyTemp) -> System.out.println(crunchifyTemp));
        }
    }
    output
    
    ==============> 1. Simple For loop Example.
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 2. New Enhanced For loop Example..
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 3. Iterator Example...
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 4. ListIterator Example...
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 5. While Loop Example....
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 6. Iterable.forEach() Example....
    Facebook
    Paypal
    Google
    Yahoo
     
    ==============> 7. Stream.forEach() Example....
    Facebook
    Paypal
    Google
    Yahoo
     
    Process finished with exit code 0

    ソース


    https://crunchify.com/how-to-iterate-through-java-list-4-way-to-iterate-through-loop/
    https://wakestand.tistory.com/432