Java设计模式

设计模式：

是一套被反复使用、多数人知晓的、经过分类编目的、代码设计经验的总结。使用设计模式是为了可重用代码、让代码更容易被他人理解、保证代码可靠性以及代码的结构更加清晰.

简单工厂模式（静态工厂模式）：

定义一个具体的工厂类负责创建一些类的创建，静态工厂模式在不改变客户端代码的情况下可以动态增加产品，明确了类的职责，但是静态工厂类如果需要增加新的对象，就需要不断地修改工厂类，不利于后期的维护

package org.westos.demo;//工厂类
public class AnimalFactory {

	private AnimalFactory() {
		super();
		// TODO Auto-generated constructor stub
	}
	public static Animal createAnimal(String animalType) {
		if (animalType.equals("dog")) {
			return new Dog();
		} else if (animalType.endsWith("cat")) {
			return new Cat();
		} else {
			return null;
		}
	}
}
package org.westos.demo;//动物类

public class Animal {
	
	public void eat() {
		
	};

}
package org.westos.demo;//猫类

public class Cat extends Animal{
	
	public void eat() {
		System.out.println("猫吃鱼");
		
	}
	

}
package org.westos.demo;//狗类

public class Dog extends Animal {
	@Override
	public void eat() {
		System.out.println("狗吃肉");
	}

}
package org.westos.demo;//测试类

public class Test {

	public static void main(String[] args) {
		
		Animal animal = AnimalFactory.createAnimal("dog");
		animal.eat();
		Animal animal2 = AnimalFactory.createAnimal("cat");
		animal2.eat();

	}

}

工厂模式

抽象工厂类负责定义创建对象的接口，具体对象的创建工作由继承抽象工厂的具体类实现

客户端不需要再负责对象的创造，从而明确了个各类的职责，如果有新的对象，只需要增加一个具体的工厂类即可，不影响已有的代码，后期维护容易，增加了系统的扩展性，但是需要额外的编写代码，增加了工作量

package org.westos.demo2;//最大的工厂类

//相当于一个大的动物工厂
public interface AinmalFactory {
	public abstract Animal creatAnimal();
	
}
package org.westos.demo2;//老虎工厂

public class TigerFactory implements AinmalFactory {

	@Override
	public Animal creatAnimal() {
		// TODO Auto-generated method stub
		return new Tiger();
	}

}
package org.westos.demo2;//狗工厂

public class DogFactory implements AinmalFactory{

	@Override
	public Animal creatAnimal() {
		
		return new Dog();
	}

}
package org.westos.demo2;//猫工厂

public class CatFactory implements AinmalFactory {

	@Override
	public Animal creatAnimal() {
		// TODO Auto-generated method stub
		return new Cat();
	}

}
package org.westos.demo2;//动物类

public abstract class Animal {

	public abstract void eat();

}
package org.westos.demo2;//猫类

public class Cat extends Animal {

	public void eat() {
		System.out.println("猫吃鱼");

	}

}
package org.westos.demo2;//狗类

public class Dog extends Animal {
	@Override
	public void eat() {
		System.out.println("狗吃肉");
	}

}
package org.westos.demo2;//老虎类

public class Tiger extends Animal {

	@Override
	public void eat() {
		System.out.println("老虎吃鸡肉");

	}

}
package org.westos.demo2;//测试类

public class Test {
	public static void main(String[] args) {
		CatFactory catFactory = new CatFactory();
		Animal cat = catFactory.creatAnimal();
		cat.eat();
		new DogFactory().creatAnimal().eat();
		new TigerFactory().creatAnimal().eat();
	}

}

单例模式

单例模式的设计思想是保证内存中只有一个对象

方法：私有化构造，本身提供一个对象，通过公共的方法让外界访问

饿汉式：

package org.westos.demo3;

public class Student {
	// 第二步：我自己在内部来创建一个对象
	//单例设计模式之饿汉式
	private static Student student = new Student();

	// 第一步：私有化构造
	private Student() {
		super();
		// TODO Auto-generated constructor stub
	}

	// 第三步：提供一个静态的公共的方法，返回这个学生对象

	public static Student getStundent() {

		return student;
	}

}
package org.westos.demo3;

public class Test {

	public static void main(String[] args) {
		
		//单例设计模式之饿汉式
		Student stundent = Student.getStundent();
		Student stundent2 = Student.getStundent();
		System.out.println(stundent == stundent2);

	}

}

懒汉式：

package org.westos.demo4;

public class Teacher {
	
	private static Teacher teacher = null;

	private Teacher() {// 1.私有化构造
		super();
	}
	// 3.提供公共的静态方法
	//  懒汉式
	public synchronized static Teacher geTeacher() {
		if (teacher == null) {
			teacher = new Teacher();
		}
		return teacher;
	}

}
package org.westos.demo4;

public class Test {

	public static void main(String[] args) {
		// 单例模式之懒汉式 体现是一种延迟加载的思想
		Teacher teacher = Teacher.geTeacher();
		Teacher teacher2 = Teacher.geTeacher();
		System.out.println(teacher == teacher2);

	}

}

Runtime类：可以执行某些DOS命令，是单例模式的应用

package org.westos.demo4;

import java.io.IOException;

public class Test2 {

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		Runtime runtime = Runtime.getRuntime();
		// exec(command); 可以执行某些DOS命令
		runtime.exec("mspaint");
		runtime.exec("calc");
	}

}

计算程序的耗时

package org.westos.demo5;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public abstract class CalcTime {

	public void calcTime() throws IOException {
		// 计算for循环的耗时
		long startTime = System.currentTimeMillis();
		// testFor();
		// testCopyFile();
		testTime();
		long endTime = System.currentTimeMillis();
		System.out.println("耗时" + (endTime - startTime) + "毫秒");
	}

	private void testCopyFile() throws FileNotFoundException, IOException {
		// 复制文件
		File file = new File("E:\\录像1.exe");
		FileInputStream fis = new FileInputStream(file);
		FileOutputStream fos = new FileOutputStream(new File("D:\\录像1.exe"));
		byte[] by = new byte[1024];
		int len = 0;
		while ((len = fis.read(by)) != -1) {
			fos.write(by, 0, len);

		}
		fis.close();
		fos.close();
	}

	private void testFor() {
		for (int i = 0; i < 100000; i++) {
			System.out.println("");
		}
	}

	public abstract void testTime();

}
package org.westos.demo5;//for循环

public class TestFor extends CalcTime{

	@Override
	public void testTime() {
		for (int i = 0; i < 100000; i++) {
			System.out.println("");
		}
		
	}

}
package org.westos.demo5;//复制文件

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class TestCopyFile extends CalcTime {

	@Override
	public void testTime() {

		try {
			// 复制文件
			File file = new File("E:\\录像1.exe");
			FileInputStream fis = new FileInputStream(file);
			FileOutputStream fos = new FileOutputStream(new File("D:\\录像1.exe"));
			byte[] by = new byte[1024];
			int len = 0;
			while ((len = fis.read(by)) != -1) {
				fos.write(by, 0, len);

			}
			fis.close();
			fos.close();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

}
package org.westos.demo5;//测试类

import java.io.IOException;

public class Test {

	public static void main(String[] args) throws IOException {
		CalcTime c= new TestFor();
		c.calcTime();
		c=new TestCopyFile();
		c.calcTime();

	}

}