使用泛型将 Java 中的集合转换为流的程序
原文:https://www . geesforgeks . org/program-to-convert-a-set-to-stream-in-Java-use-generics/
Java Set 是 java.util 包的一部分，扩展了 java.util.Collection 接口。它不允许使用重复元素，最多只能容纳一个空元素。
一个流是一个支持各种方法的对象序列，这些方法可以被流水线化以产生期望的结果。
以下是将设置转换为流的各种方法。
-
Using Collection.stream(): This method involves directly converting the Set to Stream using Collection.stream() method.
算法:
- 获取要转换的集合。
- 将集合转换为流。这是使用 Set.stream()完成的。
- 返回/打印流。
```java // Java Program to convert // Set to Stream in Java 8
import java.util.; import java.util.stream.; import java.util.function.*;
class GFG {
// Generic function to convert a set to stream private static Stream convertSetToStream(Set set) { return set.stream(); }
// Main method public static void main(String args[]) { // Create a set of String Set setOfInteger = new HashSet<>( Arrays.asList(2, 4, 6, 8, 10));
// Print the set of Integer System.out.println("Set of Integer: " + setOfInteger);
// Convert Set of Stream Stream streamOfInteger = convertSetToStream(setOfInteger);
// Print the Stream of Integer System.out.println("Stream of Integer: " + Arrays.toString( streamOfInteger.toArray())); } } ```
Output:
```java Set of Integer: [2, 4, 6, 8, 10] Stream of Integer: [2, 4, 6, 8, 10]
```
-
Using Predicate to filter the Stream: In this method filter(Predicate) method is used that returns a stream consisting of elements that match the given predicate condition. The Functional Interface Predicate is defined in the java.util.Function package and can therefore be used as the assignment target for a lambda expression or method reference. It improves manageability of code, helps in unit-testing them separately
算法:
- 获取要转换的集合。
- 通过使用预定义的静态方法或通过重写谓词接口创建新方法来定义谓词条件。在这个程序中，接口被覆盖以匹配以“G”开头的字符串。
- 将集合转换为流。这是使用 Set.stream()完成的。
- 使用定义的谓词条件过滤获得的流
- 已获得所需的流。返回/打印流。
```java // Java Program to convert // Set to Stream in Java 8
import java.util.; import java.util.stream.; import java.util.function.*;
class GFG {
// Generic function to convert a set to stream private static Stream convertSetToStream(Set set, Predicate predicate) { return set.stream() .filter(predicate); }
// Main method public static void main(String args[]) { // Create a set of String Set setOfString = new HashSet<>( Arrays.asList("GeeksForGeeks", "A computer portal", "for", "Geeks"));
// Print the set of String System.out.println("Set of String: " + setOfString);
// Create the predicate for item starting with G Predicate predicate = new Predicate() { @Override public boolean test(String s) { // filter items that start with "G" return s.startsWith("G"); } };
// Convert Set of Stream Stream streamOfString = convertSetToStream(setOfString, predicate);
// Print the filter Stream of String System.out.println("Stream from List with items" + " starting with G: ");
System.out.println(Arrays.toString( streamOfString.toArray())); } } ```
Output:
```java Set of String: [for, Geeks, GeeksForGeeks, A computer portal] Stream from List with items starting with G: [Geeks, GeeksForGeeks]
```
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