从 Java 的数组列表中移除重复的元素

原文:https://www . geesforgeks . org/remove-repeated-elements-from-ArrayList-in-Java/

先决条件:Java 中的数组列表

给定一个数组列表，任务是删除 Java 中数组列表的重复元素。

例:

Input: ArrayList = [1, 2, 2, 3, 4, 4, 4] 
Output: [1, 2, 3, 4] 

Input: ArrayList = [12, 23, 23, 34, 45, 45, 45, 45, 57, 67, 89] 
Output: [12, 23, 34, 45, 57, 67, 89]

以下是在 Java 中移除数组列表中重复元素的各种方法:

• Using a Set: Since Set is a collection which do not includes any duplicate elements. Hence the solution can be achieved with the help of a Set.

  方法:

  1. Gets an array list with duplicate elements.
  2. Convert an array list to a collection.
  3. Now convert the collection back to an array list. This will delete all duplicate elements.

  下面是上面方法的实现:

  ```java // Java code to illustrate remove duolicate // of ArrayList using hashSet<> method

  import java.util.*;

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

  // create a ArrayList String type         ArrayList             gfg = new ArrayList();

  // Initialize an ArrayList         gfg.add("Geeks");         gfg.add("for");         gfg.add("Geeks");

  // print ArrayList         System.out.println("Original ArrayList : "                            + gfg);

  // -----Using LinkedHashSet-----         System.out.println("\nUsing LinkedHashSet:\n");

  // create a set and copy all value of list         Set set = new LinkedHashSet<>(gfg);

  // create a list and copy all value of set         List gfg1 = new ArrayList<>(set);

  // print ArrayList         System.out.println("Modified ArrayList : "                            + gfg1);

  // -----Using HashSet-----         System.out.println("\nUsing HashSet:\n");

  // create a set and copy all value of list         Set set1 = new HashSet<>(gfg);

  // create a list and copy all value of set         List gfg2 = new ArrayList<>(set);

  // print ArrayList         System.out.println("Modified ArrayList : "                            + gfg2);     } } ```

  输出:

  ```java Original ArrayList : [Geeks, for, Geeks]

  Using LinkedHashSet:

  Modified ArrayList : [Geeks, for]

  Using HashSet:

  Modified ArrayList : [Geeks, for]

  ```

• 使用 Java 8 Lambdas:

  方法:

  1. Get ArrayList with duplicate elements.
  2. Use the Stream () method to convert the array list into a stream.
  3. Use the distinct () method to set the filter condition to distinct.
  4. Use the Collect () method to collect the filtered values as a list. The list will have the of duplicate elements.

  删除，下面是上述方法的实现:

  示例:

  ```java // Java code to illustrate remove duolicate // of ArrayList using hashSet<> method

  import java.util.*; import java.util.stream.Collectors;

  public class GFG {     public static void main(String args[])     {         // create a ArrayList String type         ArrayList             gfg = new ArrayList();

  // Initialize an ArrayList         gfg.add("Geeks");         gfg.add("for");         gfg.add("Geeks");

  // print ArrayList         System.out.println("Original ArrayList : "                            + gfg);

  // create a list and copy all distinct value of list         List gfg1 = gfg.stream()                                 .distinct()                                 .collect(Collectors.toList());

  // print modified list         System.out.println("Modified List : " + gfg1);     } } ```

  输出:

  ```java Original ArrayList : [Geeks, for, Geeks] Modified List : [Geeks, for]

  ```

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