【Java 8 新特性】Java 8 Runnable和Callable使用Lambda表达式示例(带参数) |
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Java 8 Runnable和Callable使用Lambda表达式示例
Java 8 Runnable Lambda示例(带参数)Java 8 Callable Lambda示例(带参数)参考文献
在
Java 8中,
Runnable和
Callable两个接口均已通过
@FunctionalInterface进行注释。
我们可以使用lambda表达式实现run()和call()方法。 在此页面上,我们还将提供如何将参数传递给Runnable和Callable方法。 Java 8 Runnable Lambda示例(带参数)Java 8支持lambda表达式。 在Java 8中,已使用@FunctionalInterface注释了Runnable接口。 现在,我们可以使用lambda表达式创建Runnable实例。 Runnable r = () -> System.out.println("Hello World!"); Thread th = new Thread(r); th.start();上面的代码等同于下面的代码。 Runnable r = new Runnable() { @Override public void run() { System.out.println("Hello World!"); } }; Thread th = new Thread(r); th.start();如果需要在run()方法中编写多行代码,可以使用如下所示的lambda表达式进行操作。 Runnable r = () -> { Consumer style = (Book b) -> System.out.println("Book Id:"+b.getId() + ", Book Name:"+b.getName()); list.forEach(style); };要将参数传递给我们的run()方法,我们应该使用final修饰符。 final List list = Arrays.asList(new Book(1, "Ramayan"), new Book(2, "Mahabharat")); Runnable r = () -> { Consumer style = (Book b) -> System.out.println("Book Id:"+b.getId() + ", Book Name:"+b.getName()); list.forEach(style); };现在,找到使用Thread类带有lambda表达式的Java 8 Runnable的完整示例。 Java8RunnableDemo.java import java.util.Arrays; import java.util.List; import java.util.function.Consumer; import com.concretepage.Book; public class Java8RunnableDemo { public static void main(String[] args) { final List list = Arrays.asList(new Book(1, "Ramayan"), new Book(2, "Mahabharat")); Runnable r1 = () -> list.forEach(Book::print); Thread th1 = new Thread(r1); th1.start(); Runnable r2 = () -> { Consumer style = (Book b) -> System.out.println("Book Id:"+b.getId() + ", Book Name:"+b.getName()); list.forEach(style); }; Thread th2 = new Thread(r2); th2.start(); } }Book.java public class Book { public int id; public String name; public Book(int id, String name){ this.id = id; this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public void print(){ System.out.println("id:"+id + ", Name:"+name); } }输出 id:1, Name:Ramayan Book Id:1, Book Name:Ramayan id:2, Name:Mahabharat Book Id:2, Book Name:Mahabharat查找示例代码以使用ExecutorService运行Runnable实例。 Java8RunnableDemoExecutor.java import java.util.Arrays; import java.util.List; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.function.Consumer; import com.concretepage.Book; public class Java8RunnableDemoExecutor { public static void main(String[] args) { final List list = Arrays.asList(new Book(1, "Ramayan"), new Book(2, "Mahabharat")); ExecutorService service = Executors.newFixedThreadPool(2); Runnable r1 = () -> list.forEach(Book::print); service.execute(r1); Runnable r2 = () -> { Consumer style = (Book b) -> System.out.println("Book Id:"+b.getId() + ", Book Name:"+b.getName()); list.forEach(style); }; service.execute(r2); } }输出 id:1, Name:Ramayan id:2, Name:Mahabharat Book Id:1, Book Name:Ramayan Book Id:2, Book Name:Mahabharat Java 8 Callable Lambda示例(带参数)Java 5中引入了Callable 接口,其中V是返回类型。 在Java 8中,Callable接口已使用@FunctionalInterface注释。 现在在Java 8中,我们可以使用lambda表达式创建Callable对象,如下所示。 Callable callableObj = () -> { return 2*3; };上面的代码等同于下面的代码片段。 Callable callableObj = new Callable() { @Override public Integer call() throws Exception { return 2*3; } };要将参数传递给我们的call()方法,我们应该使用final修饰符。 final int val = 10; Callable callableObj = () -> { return 2*val; };现在,找到使用ExecutorService带有lambda表达式的Callable的完整示例。 Java8CallableDemo.java import java.util.Arrays; import java.util.List; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class Java8CallableDemo { public static void main(String[] args) { final List integers = Arrays.asList(1,2,3,4,5); Callable callableObj = () -> { int result = integers.stream().mapToInt(i -> i.intValue()).sum(); return result; }; ExecutorService service = Executors.newSingleThreadExecutor(); Future future = service.submit(callableObj); Integer result=0; try { result = future.get(); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } System.out.println("Sum = "+result); } }输出 Sum = 15 参考文献【1】Java 8 Runnable and Callable Lambda Example with Argument |
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