자바의 정석 기초편 코드 분석 139(예제 13-15)

[ ] 자바의 정석 기초편 카테고리
chapter 13 쓰레드
chapter 13-4 쓰레드의 구현과 실행 예제
예제 13-1

[ ] 코드 분석
1. 원본 코드

import java.util.ArrayList;

class Customer implements Runnable {
	private Table  table;
	private String food;

	Customer(Table table, String food) {
		this.table = table;  
		this.food  = food;
	}

	public void run() {
		while(true) {
			try { Thread.sleep(10);} catch(InterruptedException e) {}
			String name = Thread.currentThread().getName();

			if(eatFood())
				System.out.println(name + " ate a " + food);
			else 
				System.out.println(name + " failed to eat. :(");
		} // while
	}

	boolean eatFood() { return table.remove(food); }
}

class Cook implements Runnable {
	private Table table;

	Cook(Table table) {	this.table = table; }

	public void run() {
		while(true) {
			int idx = (int)(Math.random()*table.dishNum());
			table.add(table.dishNames[idx]);
			try { Thread.sleep(100);} catch(InterruptedException e) {}
		} // while
	}
}

class Table {
	String[] dishNames = { "donut","donut","burger" };
	final int MAX_FOOD = 6;
	private ArrayList<String> dishes = new ArrayList<>();
	public synchronized void add(String dish) { // synchronized를 추가
		if(dishes.size() >= MAX_FOOD)	
			return;
		dishes.add(dish);
		System.out.println("Dishes:" + dishes.toString());
	}

	public boolean remove(String dishName) {
		synchronized(this) {	
			while(dishes.size()==0) {
				String name = Thread.currentThread().getName();
				System.out.println(name+" is waiting.");
				try { Thread.sleep(500);} catch(InterruptedException e) {}	
			}

			for(int i=0; i<dishes.size();i++)
				if(dishName.equals(dishes.get(i))) {
					dishes.remove(i);
					return true;
				}
		} // synchronized

		return false;
	}

	public int dishNum() { return dishNames.length; }
}

class Ex13_14 {
	public static void main(String[] args) throws Exception {
		Table table = new Table(); // 여러 쓰레드가 공유하는 객체

		new Thread(new Cook(table), "COOK").start();
		new Thread(new Customer(table, "donut"),  "CUST1").start();
		new Thread(new Customer(table, "burger"), "CUST2").start();

		Thread.sleep(5000);
		System.exit(0);
	}
}

2. 해석본

import java.util.ArrayList;
// java.util.ArrayList 클래스 import 한다.

class Customer implements Runnable {
// Runnable 클래스를 상속하는 Customer 클래스 선언
	private Table table;
    // 
	private String food;
	// 

	Customer(Table table, String food) {
		this.table = table;  
		this.food  = food;
	}

	public void run() {
    // 접근제어자 public으로 리턴값이 없는 run 메서드 선언
		while(true) {
        // while문 선언
			try { Thread.sleep(10);} catch(InterruptedException e) {}
			String name = Thread.currentThread().getName();

			if(eatFood())
				System.out.println(name + " ate a " + food);
			else 
				System.out.println(name + " failed to eat. :(");
		} // while
	}

	boolean eatFood() { return table.remove(food); }
}

class Cook implements Runnable {
// Runnable 클래스를 선언하는 Cook 클래스 선언
	private Table table;

	Cook(Table table) {	this.table = table; }

	public void run() {
    // 접근제어자 public으로 리턴값이 없는 run() 함수 선언
		while(true) {
			int idx = (int)(Math.random()*table.dishNum());
			table.add(table.dishNames[idx]);
			try { Thread.sleep(100);} catch(InterruptedException e) {}
		} // while
	}
}

class Table {
	String[] dishNames = { "donut","donut","burger" };
	final int MAX_FOOD = 6;
	private ArrayList<String> dishes = new ArrayList<>();
	public synchronized void add(String dish) { // synchronized를 추가
		if(dishes.size() >= MAX_FOOD)	
			return;
		dishes.add(dish);
		System.out.println("Dishes:" + dishes.toString());
	}

	public boolean remove(String dishName) {
		synchronized(this) {	
			while(dishes.size()==0) {
				String name = Thread.currentThread().getName();
				System.out.println(name+" is waiting.");
				try { Thread.sleep(500);} catch(InterruptedException e) {}	
			}

			for(int i=0; i<dishes.size();i++)
				if(dishName.equals(dishes.get(i))) {
					dishes.remove(i);
					return true;
				}
		} // synchronized

		return false;
	}

	public int dishNum() { return dishNames.length; }
}

class Ex13_14 {
	public static void main(String[] args) throws Exception {
		Table table = new Table(); // 여러 쓰레드가 공유하는 객체

		new Thread(new Cook(table), "COOK").start();
		new Thread(new Customer(table, "donut"),  "CUST1").start();
		new Thread(new Customer(table, "burger"), "CUST2").start();

		Thread.sleep(5000);
		System.exit(0);
	}
}