1.jdk，数据类型，运算符

秒速五厘米 2024-04-01 19:21 25阅读 0赞

**Java语言跨平台性的解释**

一次编译，到处运行

将.java文件编译成.class文件，然后就可以在linux，windows运行。

java的跨平台的实现是通过在不同的操作系统上的不同的jvm差异来实现跨平台的

**jdk**

jdk = jre（jvm+javase核心类库）+java开发工具

**一个源文件最多只能有一个public类，其他类不限，每一类编译后都有一个class文件。文件名必须是和public的这个类名一样**

**转义字符**

![efa88303cf7e44c0b1620e57556897d8.png][]

**注释**

单行// 多行/\* 不可嵌套 \*/ 文档注释

**基本类型**

**Java****语言有几种基本类型，分别是什么？**

Java语言提供了八种基本类型。六种数字类型（四个整数型，两个浮点型），一种字符类型，还有一种布尔型。

byte 数据类型是8位，2字节

short 数据类型是 16 位，4字节

int 数据类型是32位。8字节

long 数据类型是 64 位，16字节

float 数据类型是单精度、32位，8字节

double 数据类型是双精度、64 位，16字节

char类型是一个单一的 16 位 Unicode 字符，占2字节16bit

boolean仅有两个值true, false在JVM中并没有提供boolean专用的字节码指令，而boolean类型数据在经过编译后在JVM中会通过int类型来表示，此时boolean数据4字节32位，而boolean数组将会被编码成Java虚拟机的byte数组，此时每个boolean数据1字节占8bit.

4.int\[\]类型是不是基本类型？

不是

**整型**

![aa7bae39c0b341989e98c1481c323c1d.png][]

![b7318bb602f7485cb0ec4605dd102551.png][]

**浮点型**

![7855dedc7ba5413693eaaf131e78e45c.png][]

陷阱

![4e739cfdc9664a4db8884dd977b5bd63.png][]

**字符型**

![165450c1140647b0b1afaf16345fec0e.png][]

![476a7f7120724f9aa5c4d99ceb832c76.png][]

![faef13afd0454bb2bd3bb5dacc602e17.png][]

![1fdc36cee2d64a1bb6c402b754c5cf0b.png][]

![e5080b1f6ae64dce9b0ef40c5d30ac6f.png][]

**布尔类型**

![a3bd562026f743debee08f5a339e298f.png][]

**API****文档**

[Java 8 中文版 - 在线API中文手册 - 码工具][Java 8 _ - _API_ -]

![96d509517694468a9f036b94c73e8406.png][]

**数据类型转换**

**小转大**

![053a47272fe04489b9daab06601e7392.png][]

![bad087e6cc164cabae1eb8e47780abd3.png][]

**大转小**

![13d70a5615c64115bd1b3e7aa18a1a0c.png][]

![f4d728a936994e9bb541d908935577f8.png][]

**类型转换练习题**

![71f9260590ca4d57a101d992039779e2.png][]

**基本数据类型转**

![958405f072294e4d835a04876e5d2d3e.png][]

![fb1c1197b3d2401d9c51c5bdc3c42fef.png][]

**算术运算符**

![22fbe01fe0de4943b8a8b1329c265297.png][]

**逻辑运算符**

**&&****，&**

![4d6671027dbc4a82bfb8c5b9a09138dc.png][]

![b35500c104fa45cebac8316d2150f818.png][]

**命名规范**

![53e3ab71100548b886ab893d46b148ce.png][]

![39eb4b76abad4232bb5614fdc4410b25.png][]

**if else**

**for**

**switch case default**

![a21151f475ee4c45b83100f28d87d8bd.png][]

![513fe8a5625f479cbffc5ff9dc2a9d32.png][]

![2553d71f2f22427f9bc3da1fec83d95b.png][]

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