从列表中移除满足Java中给定谓词的元素 _removeAll

下面是有效地从满足谓词条件的列表中删除元素的方法：

p==> Predicate, specifying the conditionl==> List, from which element to be removed

使用迭代器
下面的程序演示了使用谓词从列表中删除空元素

// Java Program to remove nulls // from a List using iterator and Predicate import java.util.function.Predicate; import java.util.*; class GFG {// Generic function to remove Null Using Iterator public static < T> List< T> removeNullUsingIterator(List< T> l, Predicate< T> p) {// Create an iterator from the l Iterator< T> itr = l.iterator(); // Find and remove all null while (itr.hasNext()) {// Fetching the next element T t = itr.next(); // Checking for Predicate condition if (p.test(t)) {// If the condition matches, // remove that element itr.remove(); } }// Return the null return l; }public static void main(String[] args) {// Create the l with null values List< String> l = new ArrayList< > ( Arrays.asList( "Geeks" , null , "forGeeks" , null , "A computer portal" )); // Print the list System.out.println( "List with null values: " + l); // Creating a Predicate condition checking for null Predicate< String> isNull = item -> Objects.nonNull(item); // Removing nulls using iterator and Predicate l = removeNullUsingIterator(l, isNull); // Print the list System.out.println( "List with null values removed: " + l); } }

输出如下：

List with null values: [Geeks, null, forGeeks, null, A computer portal]List with null values removed: [Geeks, forGeeks, A computer portal]

使用List.removeAll()
在此方法中, 包含要删除元素的集合用于从原始l中删除那些元素。它要求使用谓词条件创建具有所需元素的集合。完成此操作后, 将在原始l中搜索此集合, 并删除其所有实例。

// Java Program to remove 10 // from a List using List.removeAll() and Predicate import java.util.function.Predicate; import java.util.*; class GFG {// Generic function to remove elements using Predicate public static < T> List< T> removeElements(List< T> l, Predicate< T> p) {// Create collection using Predicate Collection< T> collection = new ArrayList< > (); for (T t : l) { if (p.test(t)) { collection.add(t); } }// Print the list System.out.println( "Collection to be removed: " + collection); // Removing 10 using List.removeAll() // passing a collection l.removeAll(collection); // Return the list return l; }public static void main(String[] args) {// Create a list with null values List< String> l = new ArrayList< > ( Arrays.asList( "1" , "10" , "15" , "10" , "12" , "5" , "10" , "20" )); // Print the list System.out.println( "Original List: " + l); // Creating a Predicate condition checking for 10 Predicate< String> is10 = i -> (i == "10" ); // Removing using Predicate l = removeElements(l, is10); // Print the list System.out.println( "Updated List: " + l); } }

输出如下：

Original List: [1, 10, 15, 10, 12, 5, 10, 20]Collection to be removed: [10, 10, 10]Updated List: [1, 15, 12, 5, 20]

使用Lambdas(Java 8)
可以在Java 8中使用Stream.filter()方法, 该方法返回由元素组成的流
【从列表中移除满足Java中给定谓词的元素】匹配给定谓词条件。

// Java Program to remove nulls // from a List using Java 8 import java.util.function.Predicate; import java.util.stream.Collectors; import java.util.*; class GFG {// Generic function to remove elements using Predicate public static < T> List< T> removeElements(List< T> l, Predicate< T> p) {// Removing nulls using Java Stream // using Predicate condition in lambda expression l = l.stream() .filter(p) .collect(Collectors.toList()); // Return the list return l; }public static void main(String[] args) {// Create a list with null values List< String> l = new ArrayList< > ( Arrays.asList( "Geeks" , null , "forGeeks" , null , "A computer portal" )); // Print the list System.out.println( "List with null values: " + l); // Creating a Predicate condition checking for null Predicate< String> isNull = i -> (i == null ); // Removing using Predicate l = removeElements(l, isNull); // Print the list System.out.println( "List with null values removed: " + l); } }

输出如下：

List with null values: [Geeks, null, forGeeks, null, A computer portal]List with null values removed: [Geeks, forGeeks, A computer portal]

使用removeIf()
顾名思义, 这是删除满足给定谓词的所有元素的直接方法。

// Java Program to remove nulls // from a List using Java 8 import java.util.function.Predicate; import java.util.*; class GFG {// Generic function to remove elements using Predicate public static < T> List< T> removeElements(List< T> l, Predicate< T> p) {// Removing nulls using Java Stream // using Predicate condition in removeIf() l.removeIf(x -> p.test(x)); // Return the list return l; }public static void main(String[] args) {// Create a list with null values List< String> l = new ArrayList< > ( Arrays.asList( "Geeks" , null , "forGeeks" , null , "A computer portal" )); // Print the list System.out.println( "List with null values: " + l); // Creating a Predicate condition checking for null Predicate< String> isNull = i -> (i == null ); // Removing using Predicate l = removeElements(l, isNull); // Print the list System.out.println( "List with null values removed: " + l); } }

输出如下：