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() {@Overridepublic 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<Book> 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<Book> list =  Arrays.asList(new Book(1, "Ramayan"), new Book(2, "Mahabharat"));
Runnable r = () -> {Consumer<Book> 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<Book> 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<Book> 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<Book> 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<Book> 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 <V>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<Integer> callableObj = () -> { return 2*3; };

上面的代码等同于下面的代码片段。

Callable<Integer> callableObj = new Callable<Integer>() {@Overridepublic 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<Integer> 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<Integer> integers =  Arrays.asList(1,2,3,4,5);Callable<Integer> callableObj = () -> {int result = integers.stream().mapToInt(i -> i.intValue()).sum();return result;};ExecutorService service =  Executors.newSingleThreadExecutor();Future<Integer> 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