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Java 中的名称规范 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2

常量与变量--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2

类与对象: ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

变量的存储特点:--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

封装: ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

之所以对外提供访问方式， ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

构造代码块。 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

This --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

static 特点:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

静态使用注意事项: ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3

静态有利有弊 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4

静态修饰的内容_有成员变量和函数。--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4

实例变量和类变量的区别: -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4

主函数的定义:------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4

冒泡排序与选择排序---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4

代码在内存中_执行顺序:---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5

示例: Person p = new Person ("zhangsan",20) ;------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5

帮助文档_API -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5

单例设计模式 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5

称为:饿汉式。 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5

懒汉式----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------6

继承:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------6

多态 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------7

内部类的访问规则: -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------7

String 字符串--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------8

包装类 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------9

日期格式化----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------9

IO 流 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------9

字符流 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------9

演示:写入文件数据---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10

演示:对已有文件的数据续写. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10

通过字符,读文件. -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------10

通过字符数组,读文件------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------11

文件的复制.-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------11

BufferedWriter 缓冲区写入器---------就是装饰类的增强效果. -------------------------------------------------------------------------------------------------------------------------------------------------------------12

装饰类设计模式.-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------13

装饰类的特点及与继承的区别 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------13

字节流---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------14

复制图片-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------14

Mp3(音乐)的复制 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------14

流 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------15

流操作的基本规律

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------16

键盘录入-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------16

File--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------17

File 类常见方法 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------17

递归 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------17

递归遍历所有文件----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------18

递归使用:加法、进制转换 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------18

Properties-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------18

字节打印流与字符打印流 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------19

Serializable ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------19

RandomAccessFile------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------19

异常------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------19

异常 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------20

异常的处理 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------20

自定义异常 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------21

特殊异常-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------21

异常的三种格式 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------21

异常在子类中重写的体现 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------21

异常总结-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------22

包 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------23

Import ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------23

Jar---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------23

多线程---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------24

线程定义方式 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------24

线程:实现方式和继承方式的区别 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------24

单线程和多线程的区别 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------25

线程状态_示意图 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------25

并发安全问题 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------25

并发安全问题__卖票示例 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------26

同步的前提 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------26

静态修饰的同步锁----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------26

死锁 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------27

等待与唤醒 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------28

多线程_多个生产者与消费者_等待与唤醒___示例--------------------------------------------------------------------------------------------------------------------------------------------------------------------28

Synchronized 升级版_Lock,Condition ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------30

Thread_interrupted(中断) -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------30

集合------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------30

List -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------31

Add 方法-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------31

LinkedList ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------32

Vector__略.. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------32

Iterator_迭代器 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------33

Set--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------33

范型 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------33

泛型的应用 -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------34

Map ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------35

HashMap__增删查判-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------35

集合的取出方式 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------35

第一种 .map.keySet 取出方式_示例-------------------------------------------------------------------------------------------------------------------------------------------------------------------36

第二种方式_map.entry ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------36

TreeMap------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------37

练习_获取字符串中字母出现的次数.--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------38

高级 for 循环 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------38

可变参数 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------39

静态导入 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------39

网络编程 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40

概述 -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40

通讯要素-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40

浏览器请求 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------40

Java 中的名称规范

常量与变量

0------------------5 1 6 4 2 8 9

1------------------1 2 6 5 4 8 9---- 4 6 5 2 2 6 5 4

2------------------1 2 4 6 5 8 9----

3------------------ 1 2 4 5 6 8 9

4------------------1 2 4

选择排序,看得我快疯了,主要是现在已经凌晨一点半

了;2020 年 4 月 20 日 01:30:06

冒泡排序与选择排序

给一个数组中的数字排序

1. 冒泡排序:通过比较每两个元素之间的大小,如果第一个大于第二个,就交互它们的位置.

2. 计较方式: 两个 for 循环,外层 for 控制数组循环次数,内层 for 控制数组中每个元素需要和其他元素循环比较的次数.

3. 需要注意的一点:外层会少循环一次,内层中,每个元素和会和其他元素都互相比较一次.

所以比较的次数也会比数组长度少一,

因为数组中比较过的元素就不需要再比较了, 所以每下一次循环还会将次数减一,

4. 说通俗点,比如一个数组有四个随机数字,用第一个数字分别和后面的三个数字相比较,

再用第二个数字分别和后面的二个数字相比较,

再用第三个数字分别和后面的一个数字相比较

每次计较结果为 true 就会交换它们之间的位置.

1. 选择排序:也是两个 for 循环,外层 for 控制数组循环的次数,内层 for 控制数组中相邻两个元素之间的比较次数.

2. 需要注意一点: 因为内层 for 是控制数组中相邻元素之间的比较,所以为了避免数组角标越界,循环的次数也会减一,

因为上一次循环前面两个数字已经比较过一次了, 所以后面的内层每次循环都会次数减一.

3. 通俗点:就是数组中所有相邻的两个元素之间比较.

代码在内存中_执行顺序:

静态代码块>开辟空间,分配地址,建立属性变量,进行默认初始化>显示初始化>构造代码块>对应构造函数>将堆内存中的地址分配给栈内存中的变量

示例: Person p = new Person ("zhangsan",20) ;

该句话都做了什么事情?

1，因为 new 用到了 Person.class.所以会先找到 Person.class 文件并加载到内存中=

2，执行该类中的 static 代码块，如果有的话，给 Person. class 类进行初始化。

3，在堆内存中开辟空间，分配内存地址。

4, 在堆内存中建立对象的特有属性。并进行默认初始化。

5, 对属性进行显示初始化。

6，对对象进行构造代码块初始化。

7, 对对象进行对应的构造函数初始化。

8，将内存地址付给栈内存中的 p 变量。

Person p = new Person();//短短这行代码发生了很多事情

1.把 Person.class 文件加载进内存

2.在栈内存中，开辟空间，存放引用变量 p

3.在堆内存中，开辟空间，存放 Person 对象

4.对成员变量进行默认的初始化

5.对成员变量进行显示初始化

6.执行构造方法（如果有构造代码块，就先执行构造代码块再执行构造方法）

7.堆内存完成

8.把堆内存的地址值赋值给变量 p ，p 就是一个引用变量，引用了 Person 对象的地址值

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