JavaPHP

老板要求的Java和PHP类比学习

一、java是什么

Java编程语言是一种高级语言，可以通过以下所有流行语来表征，同时相比PHP，使用❎⛔️✅：

Simple【简单】❎
Object oriented【面向对象】⛔️
Distributed 【分布式】✅
Multithreaded【多线程】✅
Dynamic【动态】❎
Architecture neutral【架构中立性】✅
Portable【可移植】⛔️
High performance【高性能】✅
Robust【强壮】✅
Secure【安全】✅

java编译过程：.java ->.class->01100，编译器是JavaVM

php编译过程：.php->opcode->01100，编译器是ZendVM

二、安装

1、Mac

// java
brew install java
// php
brew install php

2、包管理

// java maven
brew install maven
// php composer
brew install composer

三、你好，世界

// HelloWorldApp.java
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}
javac HelloWorldApp.java
java HelloWorldApp

// HelloWorldApp.php
<?php
    echo "Hello World!";
php HelloWorldApp.php

四、面向对象概述

对象object：类似现实世界的对象，他们都拥有状态和关系行为。一个对象存储他们的状态在一个变量和暴露他们的行为通过方法

封装encapsulation：隐藏状态并通过方法进行交互

类class：我们经常会讲到new一个对象，解读为对象是类的实例，类是对象的蓝图

继承inherit：继承来自父类的状态和方法

接口interface：制定一套规范方法给类使用

包package：命名空间，类似电脑中的文件夹

五、语言基础

1、变量

变量种类

实例变量⛔️
静态变量✅
常量⛔️
参数⛔️

主要数据类型

// java
float pi = 3.14;
// php
$pi = 3.14;

byte
short
int
long
float
double
boolean
char

数组

// java
int[] arr = {1,2,3};
int[][] array = {
    {1,2,3},
    {4,5,6},
    {7,8,9}
};
// php
$arr = [1,2,3];
$array = [
    [1,2,3],
    [4,5,6],
    [7,8,9]
];

###2、运算符

java和php⛔️

###3、表达式

java和php⛔️

4、流程控制

java和php⛔️

六、类与对象

1、类概述

public class Bicycle {

    // 预定义变量
    public int cadence;
    public int gear;
    public int speed;

    // 构造函数
    public Bicycle(int startCadence, int startSpeed, int startGear) {
        gear = startGear;
        cadence = startCadence;
        speed = startSpeed;
    }

    // 设置踏板
    public void setCadence(int newValue) {
        cadence = newValue;
    }

    // 设置齿轮
    public void setGear(int newValue) {
        gear = newValue;
    }

    // 减速
    public void applyBrake(int decrement) {
        speed -= decrement;
    }

    // 加速
    public void speedUp(int increment) {
        speed += increment;
    }
}

public class MountainBike extends Bicycle {

    public int seatHeight;

    public MountainBike(int startHeight, int startCadence, int startSpeed, int startGear){
        super(startCadence, startSpeed, startGear);
        seatHeight = startHeight;
    }

    public void setHeight(int newValue) {
        seatHeight = newValue;
    }

}

<?php
class Bicycle
{
    // 预定义变量
    public $cadence;
    public $speed;
    public $gear;

	// 构造函数
    public function __construct(int $startCadence, int $startSpeed, int $startGear)
    {
        $this->cadence = $startCadence;
        $this->speed = $startSpeed;
        $this->gear = $startGear;
    }

    // 设置踏板
    public function setCadence(int $newValue)
    {
        $this->cadence = $newValue;
    }

    // 设置齿轮
    public function setGear(int $newValue)
    {
        $this->gear = $newValue;
    }

    // 减速
    public function applyBrake(int $decrement)
    {
        $this->speed -= $decrement;
    }

    // 加速
    public function speedUp(int $increment)
    {
        $this->speed += $increment;
    }
}

<?php
class MountainBike extends Bicycle
{
    public $seatHeight;

    public function __construct(int $startHeight, int $startCadence, int $startSpeed, int $startGear)
    {
        parent::__construct($startCadence, $startSpeed, $startGear);
        $this->seatHeight = $startHeight;
    }


    public function setHeight(int $newValue)
    {
        $this->seatHeight = $newValue;
    }
}

2、对象

public static void main(String[] args) {
    // 实例化对象
    Bicycle myBike = new Bicycle(30, 0, 8);

    System.out.println(myBike.cadence+" "+myBike.gear+" "+myBike.speed);
}

// 实例化对象
$bicycle = new Bicycle(30, 0, 8);

echo $bicycle->cadence." ".$bicycle->speed." ".$bicycle->gear."\n";

3、类进阶

// java可以有多个构造函数，根据参数不同而生成的对象不同
public class Rectangle {
    private int x, y;
    private int width, height;
        
    public Rectangle() {
        this(0, 0, 1, 1);
    }
    public Rectangle(int width, int height) {
        this(0, 0, width, height);
    }
    public Rectangle(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }
    
}

4、类嵌套

public class ShadowTest {

    public int x = 0;

    class FirstLevel {

        public int x = 1;

        void methodInFirstLevel(int x) {
            System.out.println("x = " + x);
            System.out.println("this.x = " + this.x);
            System.out.println("ShadowTest.this.x = " + ShadowTest.this.x);
        }
    }

    public static void main(String... args) {
        ShadowTest st = new ShadowTest();
        ShadowTest.FirstLevel fl = st.new FirstLevel();
        fl.methodInFirstLevel(23);
    }
}
x = 23
this.x = 1
ShadowTest.this.x = 0

5、枚举

public enum Day {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
    THURSDAY, FRIDAY, SATURDAY 
}

七、注解

1、替代注释

public class Generation3List extends Generation2List {

   // Author: John Doe
   // Date: 3/17/2002
   // Current revision: 6
   // Last modified: 4/12/2004
   // By: Jane Doe
   // Reviewers: Alice, Bill, Cindy

   // class code goes here
}

@interface ClassPreamble {
   String author();
   String date();
   int currentRevision() default 1;
   String lastModified() default "N/A";
   String lastModifiedBy() default "N/A";
   // Note use of array
   String[] reviewers();
}

@ClassPreamble (
   author = "John Doe",
   date = "3/17/2002",
   currentRevision = 6,
   lastModified = "4/12/2004",
   lastModifiedBy = "Jane Doe",
   // Note array notation
   reviewers = {"Alice", "Bob", "Cindy"}
)
public class Generation3List extends Generation2List {

// class code goes here

}

2、预定义注解

@Deprecated
@Override
@SuppressWarnings
@SafeVarargs
@FunctionalInterface
@Retention
@Documented
@Target
@Inherited
@Repeatable

八、接口和继承

1、接口

// java
// 接口继承接口
public interface GroupedInterface extends Interface1, Interface2, Interface3 {
    // code
}
// 实现接口
public class RectanglePlus implements Relatable {
    // code
}

// php
interface GroupedInterface
{
    // code
}
class RectanglePlus implements Relatable
{
    // code
}

2、继承

// java
public class Bicycle {
    // code
}
public class MountainBike extends Bicycle {
    // code
}
public class Pegasus extends Horse implements Flyer, Mythical {
    // code
}

// php
class Bicycle {
    // code
}
class MountainBike extends Bicycle {
    // code
}
class Pegasus extends Horse implements Flyer, Mythical {
    // code
}

3、多态

public class MountainBike extends Bicycle {
    // 通过重载实现多态
    public void printDescription() {
        super.printDescription();
        System.out.println("The " + "MountainBike has a" +
            getSuspension() + " suspension.");
    }
}

4、对象作为超类

protected Object clone() throws CloneNotSupportedException
public boolean equals(Object obj)
protected void finalize() throws Throwable
public int hashCode()
public String toString()

5、抽象方法

public abstract class GraphicObject {
   abstract void draw();
}

abstract class GraphicObject {
   abstract function draw();
}

九、数字和字符串

1、数字类

Class Number

2、字符类

Class Character

3、字符串类

Class String

4、装箱和拆箱

todo

十、泛型

1、为什么使用泛型

// 普通写法 需要强制转换
List list = new ArrayList();
list.add("hello");
String s = (String) list.get(0);

// 泛型写法 不需要强制转换
List<String> list = new ArrayList<String>();
list.add("hello");
String s = list.get(0);

2、泛型类型

通常使用的类型变量名字：

E - Element (used extensively by the Java Collections Framework)
K - Key
N - Number
T - Type
V - Value
S,U,V etc. - 2nd, 3rd, 4th types

十一、异常处理

public class ListOfNumbers {

    private List<Integer> list;
    public static final int SIZE = 10;

    public ListOfNumbers() {
        list = new ArrayList<Integer>(SIZE);
        for (int i = 0; i < SIZE; i++) {
            list.add(new Integer(i));
        }
    }

    public void writeList(){
        PrintWriter out = null;
        try {
            System.out.println("Entered try statement");
            out = new PrintWriter(new FileWriter("src/HelloWorldApp/OutFile.txt"));

            for (int i = 0; i < SIZE; i++) {
                out.println("Value at: " + i + " = " + list.get(i));
            }
        } catch (IndexOutOfBoundsException e) {
            System.err.println("IndexOutOfBoundsException: " + e.getMessage());
        } catch (IOException e) {
            System.err.println("Caught IOException: " + e.getMessage());
        } finally {
            if (out != null) {
                System.out.println("Closing PrintWriter");
                out.close();
            } else {
                System.out.println("PrintWriter not open");
            }
        }
    }

    public static void main(String[] args) {
        ListOfNumbers numbers = new ListOfNumbers();
        numbers.writeList();
    }
}

十二、基本输入输出

public class CopyBytes {
    public static void main(String[] args) throws IOException {
        FileInputStream in = null;
        FileOutputStream out = null;

        try {
            in = new FileInputStream("src/HelloWorldApp/xanadu.txt");
            out = new FileOutputStream("src/HelloWorldApp/outagain.txt");

            int c;
            while ((c = in.read()) != -1) {
                out.write(c);
            }
        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }
}

十三、并发

1、线程对象

// 方法1
public class HelloRunnable implements Runnable {
    @Override
    public void run() {
        System.out.println("Hello from a thread!");
    }

    public static void main(String[] args) {
        (new Thread(new HelloRunnable())).start();
    }
}
// 方法2
public class HelloThread extends Thread {

    @Override
    public void run() {
        System.out.println("Hello from a thread!");
    }

    public static void main(String[] args) {
        (new HelloThread()).start();
    }
}

JavaPHP

一、java是什么

二、安装

1、Mac

2、包管理

三、你好，世界

四、面向对象概述

五、语言基础

1、变量

变量种类

主要数据类型

数组

4、流程控制

六、类与对象

1、类概述

2、对象

3、类进阶

4、类嵌套

5、枚举

七、注解

1、替代注释

2、预定义注解

八、接口和继承

1、接口

2、继承

3、多态

4、对象作为超类

5、抽象方法

九、数字和字符串

1、数字类

2、字符类

3、字符串类

4、装箱和拆箱

十、泛型

1、为什么使用泛型

2、泛型类型

十一、异常处理

十二、基本输入输出

十三、并发

1、线程对象

About

Languages