內容目錄

Difference Between Thread and Runnable in Java

多執行緒實現同時執行多任務，有兩種方式可以實現，一個是繼承 Thread ，覆寫 run 方法，另一個是實作 Runnable 介面，Difference Between Runnable and Thread in Java 提供這兩種應用方式，本篇增加了範例，並透過單元測試來驗證產出結果。

檔案目錄

./
   +- src
       +- test
       |   +- org
       |       +- ruoxue
       |           +- java_147
       |               +- multithreading
       |                   +- runnable
       |                      +- DifferenceThreadRunnableTest.java

單元測試

Difference Between Thread and Runnable in Java 提供執行任務等操作。

task

Difference Between Thread and Runnable 繼承 Thread ，覆寫 run 方法，建立 1 條執行緒，執行 1 個任務，每個任務耗時 3 秒完成。

	protected class Task extends Thread {

		@Override
		public void run() {
			try {
				System.out.println("T[" + Thread.currentThread().getId() + "] worker: ready");
				TimeUnit.SECONDS.sleep(3);
				System.out.println("T[" + Thread.currentThread().getId() + "] worker: finished");
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}

	}

	@Test
	public void task() {
		Thread thread = new Task();
		thread.start();

		try {
			thread.join();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}

T[11] worker: ready
T[11] worker: finished

worker

Difference Between Thread and Runnable 繼承自定義物件，並實作 Runnable 建立 1 條執行緒，執行 1 個任務，每個任務耗時 3 秒完成。

	protected class Obj {
		private String name;

		public Obj(String name) {
			this.name = name;
		}

		public String getName() {
			return name;
		}
	}

	protected class Worker extends Obj implements Runnable {

		public Worker(String name) {
			super(name);
		}

		@Override
		public void run() {
			try {
				System.out.println("T[" + Thread.currentThread().getId() + "] worker " + getName() + ": ready");
				TimeUnit.SECONDS.sleep(3);
				System.out.println("T[" + Thread.currentThread().getId() + "] worker " + getName() + ": finished");
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}
	}

	@Test
	public void worker() {
		Worker worker = new Worker("AAA");
		Thread thread = new Thread(worker);
		thread.start();

		try {
			thread.join();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}

T[11] worker AAA: ready
T[11] worker AAA: finished

threadsWorker

Difference Between Thread and Runnable 繼承自定義物件，並實作 Runnable ，建立 3 條執行緒，執行相同任務，每個任務耗時 3 秒完成。

	@Test
	public void threadsWorker() {
		try {
			int taskSize = 3;
			Worker worker = new Worker("BBB");
			List<Thread> threads = new ArrayList<Thread>();
			IntStream.range(0, taskSize).forEach(e -> {
				Thread thread = new Thread(worker);
				thread.start();
				threads.add(thread);
			});

			threads.forEach(e -> {
				try {
					e.join();
				} catch (InterruptedException ex) {
					ex.printStackTrace();
				}
			});
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}

T[11] worker BBB: ready
T[13] worker BBB: ready
T[12] worker BBB: ready
T[12] worker BBB: finished
T[13] worker BBB: finished
T[11] worker BBB: finished

DifferenceThreadRunnableTest.java

Difference Between Runnable and Thread 新增單元測試，驗證是否符合預期。

package org.ruoxue.java_147.multithreading.runnable;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.stream.IntStream;

import org.junit.Test;

public class DifferenceThreadRunnableTest {

	protected class Task extends Thread {

		@Override
		public void run() {
			try {
				System.out.println("T[" + Thread.currentThread().getId() + "] worker: ready");
				TimeUnit.SECONDS.sleep(3);
				System.out.println("T[" + Thread.currentThread().getId() + "] worker: finished");
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}

	}

	@Test
	public void task() {
		Thread thread = new Task();
		thread.start();

		try {
			thread.join();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}

	protected class Obj {
		private String name;

		public Obj(String name) {
			this.name = name;
		}

		public String getName() {
			return name;
		}
	}

	protected class Worker extends Obj implements Runnable {

		public Worker(String name) {
			super(name);
		}

		@Override
		public void run() {
			try {
				System.out.println("T[" + Thread.currentThread().getId() + "] worker " + getName() + ": ready");
				TimeUnit.SECONDS.sleep(3);
				System.out.println("T[" + Thread.currentThread().getId() + "] worker " + getName() + ": finished");
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}
	}

	@Test
	public void worker() {
		Worker worker = new Worker("AAA");
		Thread thread = new Thread(worker);
		thread.start();

		try {
			thread.join();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}

	@Test
	public void threadsWorker() {
		try {
			int taskSize = 3;
			Worker worker = new Worker("BBB");
			List<Thread> threads = new ArrayList<Thread>();
			IntStream.range(0, taskSize).forEach(e -> {
				Thread thread = new Thread(worker);
				thread.start();
				threads.add(thread);
			});

			threads.forEach(e -> {
				try {
					e.join();
				} catch (InterruptedException ex) {
					ex.printStackTrace();
				}
			});
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

心得分享

Difference Between Thread and Runnable Interface in Java 的區別：

Thread Class	Runnable Interface
是一個類別	是一個介面
有很多種方法，包含 start 、run 方法	只有一個抽象方法 run
每一個執行緒建立一個物件並與之相關	多個執行緒可以共享同一物件
需要更多記憶體	需要較少記憶體
繼承後，無法再繼承其他物件	實作介面，可以繼承其他物件