Misty rain
言必行,行必果。
java入门篇---java中的数据类型和运算符
10/14
前言： 在java编程中，我们需要定义数据类型和进行一些数据运算，本篇介绍java中常用的数据类型和基本运算符，包括如何写一段赏心悦目的代码。
java开发工具：
Eclipse 官网http://www.eclipse.org/downloads/下载64/32位
JDK 下载http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-138363.html下载
配置JDK教程:https://jingyan.baidu.com/article/bea41d435bc695b4c41be648.html //百度经验
Eclipse的基本使用这里就不做介绍了，需要的朋友请留言，谢谢。
有了工具，如何写一段赏心悦目的代码呢？
很简单
上下对比可以发现 A代码显得很潦倒，而B代码则整齐一目了然。其实很简单Ctrl+Shift+f即可对其。
进入正题：
变量与常量-- ##
从名字可以看出来 变量当然是属于可变的，常量是一旦固定不可变的，也是java必须要掌握的俩个量。
怎么定义？
public static void main(String[] args) {
int a = 2;//变量
String userName="哈哈";//变量
final int KEY=1;//常量
a=3;
System.out.println(a);
}常量一般用final修饰且不可变。变量可以改变。
说到这里，我们简单介绍一下其他的命名规范:
类名--首字母大写 MainActivit{};方法名--首单词字母小写后续大写 userName();
关键字不可命名其中任何一类-- 查看所有关键字
注释代码--
分为单行注释和多行注释(文档注释）
Ctrl+/ 单行 Ctrl+Shift+/ 注释 Ctrl+Shift+ 取消文档注释
数据类型
通常，有了数据当然会有属于类型，就比如汽车，火车都属于交通类型，数据亦是如此。
字符类型char，布尔类型boolean以及数值类型byte、short、int、long、float、double。
其中布尔只有true false俩种，任何数据运算也只会返回这俩种结果，比如2<3? 返回true 数值类型float double；double相对于float更为精确，俩者又被成为浮点类型。
浮点型运算中要注意：
System.out.println(3.3f+2.3d);
这句话输出为5.599999952316284 而将d改为f则为5.6 导致计算不精准。f则代表float类型d则double 不写后缀则默认int类型
说到运算，又到了算术运算符:
int a = 2;
int b = 2;
float c=3.2f;
System.out.println(a+b);
System.out.println(c-b);
System.out.println(a*c);
System.out.println(a/b);
System.out.println(c%b);
如图。可能有的没见过，以后的系列中会逐一叙述到。
在此，又引入逻辑运算符、关系运算符：
1、我认为多运用于条件判断：
int a=1;
int b=2;
int c=2;
if(a!=b&&b==c){
System.out.println("条件成立");
}
if(a!=b||b!=c){
System.out.println("条件成立");
}
System.out.println(a<b);
System.out.println(!(a<b));逻辑与--&&(条件同时满足为true) 逻辑或--||(条件一真则真) 逻辑非--！(相反结果 !true==false)
2、关系运算符很简单 一张图:
{!{data:image/webp;base64,UklGRooXAABXRUJQVlA4WAoAAAAwAAAADwQAKwEASUNDUBgCAAAAAAIYAAAAAAQwAABtbnRyUkdCIFhZWiAAAAAAAAAAAAAAAABhY3NwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAA9tYAAQAAAADTLQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAlkZXNjAAAA8AAAAHRyWFlaAAABZAAAABRnWFlaAAABeAAAABRiWFlaAAABjAAAABRyVFJDAAABoAAAAChnVFJDAAABoAAAAChiVFJDAAABoAAAACh3dHB0AAAByAAAABRjcHJ0AAAB3AAAADxtbHVjAAAAAAAAAAEAAAAMZW5VUwAAAFgAAAAcAHMAUgBHAEIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFhZWiAAAAAAAABvogAAOPUAAAOQWFlaIAAAAAAAAGKZAAC3hQAAGNpYWVogAAAAAAAAJKAAAA+EAAC2z3BhcmEAAAAAAAQAAAACZmYAAPKnAAANWQAAE9AAAApbAAAAAAAAAABYWVogAAAAAAAA9tYAAQAAAADTLW1sdWMAAAAAAAAAAQAAAAxlblVTAAAAIAAAABwARwBvAG8AZwBsAGUAIABJAG4AYwAuACAAMgAwADEANkFMUEjnEgAAASFFbdtA6rvhT7g7GUT0fwL0jTtSTBJWNYkg22b1B/8RImICuiIo32rRrLBt2yb/n57uyYgJMNO2jYsg/0bAE///axpt+xe8tEenpQz1dqYMVh07xk93P8/LZXVdK3e/Vr7za+XutnT3w2X66EmRMHRKoNDiroVH8v0m+UqAkCwaERQlWQ1bS9Kr1NplabGjjAEd7gfEwP/xH//xH//xH//xH//xH//xH//xH//xH/9d+d+u/G9X/jf++6S68r9Z3I9P8dqd5ziNkr3YN1mukoKhpK0kbCSuVUSs8byRzmtvbdW9teXe2tqYWJZF6+wslclklt78vOFv3tS22keYJ9Wtmze3HJPUUvmPj2tY7Ss/8XgSWywDo4bVfvUHJ7TkUk+7ahGffCsZMmmcH8CiK1nC+RFQshf/JstVUjCUtJWEjcS1Ctsa24bLaJFZGg4N6+MHf1UiURZ/ET99eXo6aSTQHz158MArZ0ov/qWIhtVc3/ANa47jt4Lxl4nJY0ksP3zw6gOnvDV/9ad/p8eLT0z3P3zzwasGBHsu3vyOtN4+dnY7sL297UMxqP76u++8e6Krj13a3g4E/DfQTHr52jvvvNvQ0cdubW/7fP4VVKPe+f+33onq5+mJgN/n9/muI5tV+f/XXnu3rJdfe/+pw+f3XZM3S2LTuX76268d6eRj527fPrh9x4JuViEUjbLRaFsfv9Z7++D2/ha6VZnjcDQafaGTOyOv3D64vbc7j2zVaeg4Eo2e6eUZCvfBwd7uDrJRbOg4FGaLevlY+8H+7t4u6v7lZSX+96HjSFs338Hc3Nvd3dudQrTp/Og4GAyW9HNV04OnS7t7blSbjo+CwWBEN5/PsLuzs7uDnKGoHh4Gg8G8Xj7WBM0XEOogEaseDg+/GjzWy8eawdhAwMigJisPnx8eHZ/r5GMtO7s7236/GTYL5S8kHB4eHh5f6uNjrTu72wG/H13p3Klxf3l4qJOLmmy7O35/wG9FNqsZikQikXBTH5c07QTAWBt6GWQQzBdp6eJjpwN+8DmFbFY7GIqEI7y+UR/PVN576PQH/Hb0/MRxEMQlHV3iF7u/l+syDHPnOVrDMAjDyHwVRjk3NzY2NoWCB+Tty5cnLzkuAW9aDPkTpXHn7fYO1S1i6VOmbLYp26f/m2GYX1O17Wd+yqrBvjrTf/MDKrZx61qsK73yrWr2O23YNdnYekHNtr/8Jk22vaVmm+sPPmWRLyOsVev1nkhH6HIlSz0CTdrIfNlRZrt92m63A2Ejuo6h2Wy0Gs2BEm+afFPinXe612y1WMRHBoptcNnvDyymdqfP/OZvqlvIL/7ED5hQrDl67/DoaMRUEW15vF6P12PCMKwWicZiMTY7GXgOs65F0adr0Ujc5kLHnog2Go1GU/q6rqqWEP/V40XEF0b4/aOjo1P0NkzbXx+f8nq8iziGJcLRWIyN9VW/6oyHjgR9yNtcvMhlwSe4rk7sPaJyL9/fP9g/QNzyjB8eHR1FhrMZvB6Px+vxYGVhI5FIjI3lZderqn6F8eCR+JwhbnMlewHIA803oaSHrt052D/YR1xOyaOj3n8W2nBXRkrgI2LlC+J862tra+try1h2Z7lEIpUq+v1+j9fjHD5ZEaX7HCJ8G0E3mIwGE2zCNgvN5IvRap6YcCTjgMzd6L4C9Vny91DPXmR5FwRmz2BSUhjfvbt/sD8PmYauMm6T6Lipr6/8xGP6+deNzc21tTW6YBi+aGskLEVq/4Qj+dWJZjZ6ecoFgA/Mns7kpp6+d+dgn0z0iaFHliASArW2nzPf8/UT705kD6DnIpsFgYj6yEOM8vfRvbt391cnbzUCzZ1I4H7AcUi2NMGurvW7d+/e29RE2ruPJsU1RqhY8e4HP7/aKNvgbpj8HRCG6V/2BwPhCGwtG2zWQbv7G29PDOtwKLVyNhLdrD5+vCCL3x8MGPiTkTPAYLG0u/0BA9slcUTLEJl84yKQNSLWLdusNpvVarNaTaRa9yydzqTB+cxA7om2O1qD14q4zEVAAqt9fmXftuhyOsx4eyXNZrPVbCl6Rcv+PLlCp98fMEaTyWQ2myxmM5DzWqxWsio+LEFGpVotVyuVMtwrlcoAE1LdoZH9Ta2urq2ugO4gCNBCin3+1Ux6fGgT1LxGZkPUMTdNL9gYG4/Hh0fdvLT0sDh3zd7q7N687pifu6aEmwH+RrkCWCPgBlwH+sh5KayursL0WSIuVXrrP197V/vhj4g+60DGhKdkYmNsLB7PDQl8lpf4DsaB3yGxNzJWpRZPHTnw1EbVAliG6LO8srIiHTUSi0pK/fgf/H9yMsXP8LzxYfqsr+Ev+hyYL3aSGyb4EL8B+TpTnjoweMROx+WoyzkDFwTCzzQVq1NcMpVKJVMXGg1+wFseos/a+joJ2Xyenw8EJfnhgg+NF7LAHPER7HWMSo376irvgED8QY0K8d8NHMcB/KS0FfzIaOeBDwLw4yTz02bYf4qxscIwwIdGwpGnjhx42qP127cLcQiMHxstl4vjOC6ZSqZKmg1+zMAHAfwhU7FwluSXOPTZGiXwKbXMZ0FJ8IzoL5+PQ0T4mafmeyU4eD4NZ69ijYcPzB8i778Cx8H4qSgbPqSr+i/OL6B+zjC9Ua5b/3gX4g/FepZyL/4/YL6MZkOfGafzSQ/CzxwRj19weSH85EaGB3LOswfmz+jPyRk8Hi84Qi5nJOMhxqGe1mLQM+90Oq+Lz0+R2fPnOC4B8HM2MuAj9kDAIhj988H8cQuW05vvBTSfinZExsNi57kjyR6CO+TngD/AD+kqFD6E3e/zzLnIAxkfa8ELjd2iaXk69iIePyE93yRf+CAgR4I9C6SVcgmIP8lUfQTA5/w8A3sgY2VFGGFPhOp8mVgMeCLnkwd5Ro5Sdn7eca8iRs8sqt14ZQ0cxB8uVVTKc1hcftgWwYcwBc8z53AkAul0xst8EH9u3cQMCQ0GPEeRjYGgRI0LmEalLmZ+ft4BjuDzUH0ADfrkGSufCQf8OVfIs1heXl5eWgbdSBY+wAOBk5Lj6Q0B+ON1Y87XM0LfkxGz8mRy4s7QFMzB1JE4b6JmfzOXz+cL4BNcpwhFsHVZgj7TZBU6ggciikTGl6sIPJFb7huYngiMHjNW5clJXCvwO2Znr90u8tQRux/yWxBkf/L5XD6fK8D0KSkmDpGAzwJh+AAXBAQiYyvshqkCIhJhPmwTIU8EeT6gN59YPREyq3GWp47M0ewsUn0wYWFQHrBHcEGA+9EAbBzmOKQmoAeORKCQe7zNB5KUt9ybsOWUyhtiwBWZgOf7yEpObrfw1TgPG0Ac0TjkKJ/wNkB5MJ16Ly9yQSS0gUqLQ4g+hpqVewvGD9ggGX/zeUFEgjUfiRK0GMvG2BcTsgT52797BeVuFPC3AUrFEuhl0VFTfFtDHYe0oRAEOp8fl2vKIkQk4vloZZKrcAnaBB2DfP4HP2ZUhv0DwJ0iDx+AHnC+KpkrGZ44BDntnsnw8IHnA3+wYGzO5/V43G73BpbZmBsZyRTcsxN3SuKnfgHxv4hUKVQbxpnTEAwfwJ6BzJNRahxCdG8yk8mI4NMYVQtJuV+TB56P1suEE+FnglcxceuEgo5KFf6U6k3FPgiDTdSfXYjiEKLlu5lMhtcpQfSB5FLjdj6vx+2+5V6nY3MqCfshZxrAdmV9GsFFbTQ6M+b0WbFWqZbL5VK5VCy1FJNOs5HoVhq59gzAD+SCDMbz0rFBjgg/HxVJMycKR7QE+dJffhMZ97XX7SEdIVqzF0Igi4QFBLRRRDcnMwJ94IQEBMmxPt8ajr3IqgWhHh3CjyYhZ3b94aPZgW1kPqTLDE8fUShSBotljM/ndUPzEd+qTHJwWkIDqXL0+7w+n881slohI8bPhQoQo/OOCIWQpJSE3JAkjx/NpW8E/AG/94ayG5mYqA13uzMePIXo0xHWhAqY75bb7fW7F4lKvrkkHI70GY2nvxII3PvIcq1gtpjN/Hn4iF6+ASFF2ibROypjFUxv3N7x3FhxWgluP3McHI60GS2rGwQgoRyhmTKzunySqcmjRWzAWJIhKVPt5XK5XNcXPe65+RlgK6GN6CTkhiRTvOhbJ+4LrusuUefTR0SFHjx84HCkPHmxR5vYUpLqSClkzL+GwIn4k9fx0KMYIZgIPVAkIrKaqPa7a4j/D5fkkmkNlz3qYEtCBB4QicxS0XrUixfJeORlLpdjmIGKZ4/mszkEwCNKRVjobQJ1zv41+H5Yx81IzAvgQUtDUClniLJslI3rsuy5LrUboRBVaYyNslG2pa+ix0h4O4KgbiHMAmdEPw1BHAv3a6JkpINGKXvXMGXDqRKPAFckoXeCZ8ax4JA8glKThDcjstls4dI8Pe9aszMzyBe/hMZWVDp4NJDSUocMeeiY3s5mc1nQc33n+gefPntkwqBUKALyE3qjMhkARwo8sl4HwaqlrNBh+OSaDMPc+uCHnj19ilMGXYbGvtAJwTOL6XoQLWDOSsFHoobZducDj3xeH461qVCEZaNZfQ48EmyQwg64TkqPRCMTWezNpN4RwUd+4sC21+e9gWN0JBQVghKdbgtyQcb1mKZ5B50i6CXx+UuGQapf3gr4vT7vDE4QEwJjWc2IPGrpTxTIkGeO6h0UZMjTwLTREgj4vD4vjmEXoXCEjaZ0MfDYIeZIsMdE8w5qRRn0dEglPwM+n9d3E8ewODS2p2tVJjtkXI8pqrFHQYY8ddJWbwa8Pq/PgXNXYWEsH5ToUyLEBce9koT3MUvzBgYCdyTRQ61A0STEJMKOBVaEEw6Fo9FT3WkDEpyHrzNQjT0KMui5pP085vxg7C0cw7hQOBSNNvSg5AOPHWn0mOE7oKRFFLgDoQcmj3IKEte9YOwSjscTBmPHXlBCzY2zTU2Bo8fPh7XdeU7JWLnY2DZls9n2YpLNE5Oy4NfUoQpZGj0kkg84BBBxR+R81BT3gAw+aKwBRwQFjY2Ncy2JTaAMdASuQzJCUl0ytP+GwNjSH/8AXlMpbyco7pBAzwyJW8D55UPckXA+FPWk5N5F9x84vD4PjmFpaGxxTDoVktfJWqISEmvfqnrIA5UdOp33SxLo4RUIVJMPlf5U6lAi/ugq/4k5A6BjjY2FwqEQOx6dCqNaessuqJXgw+lcEI7466D/gZXmDbSgtKNwBF9XHZYnB6qeAgF/IODCeSC8KwL2LEaiINRitljE5x+E0J0K9Zh3e0s9NIE5UkckShEx6oz5iENwOXjuiOBTGsLnNw08Eb/XjmFYDhqbHsqvFvCEwnm5PMu2IpYmzTXVbrXard4rjmSpp8RgUnjQEs8bXwNHNTl22b8cGM3t3kCczrJaBCPEFvz2r4/1trT0oCbBHhnrCad+IPIA9wM6GgzxY1wN+AN+3xaOYS+hsQNl/GgANyicH5JlSHUjCcKM9HWyRnQV98YQFjx48UEzKS0+aDaaDdkj0UyqRNb6oyD9sCCUI9P7kqu1SrVardaqlVq1VrtUwPYV3W0z6IWyubm5sb4+hyNsbGf//zSRWAlsB7b52AXrCQQBT4icp7bahtypEGFF8jpZS4Yil6ow8vQhvCASR1UFZn/59SaVpjcZ/U5Fn97zoC4446kjBZ9Zas+01J9ORBGg01WJC/bkptoGjALevt1etwud7xrmFk7SVVTQDEbIg5qSJg+98DdfkOx1hlGzAtWBmkcK4AmF85dD8Tzpx4ky5KHm9tbz0uxR0z+GP/g2Vdh6gCHkzw93Ck1xGciZmemZDyXF5HFQy6Tk8/mCBHwuVfvL0fXT32DsdDqdbnew4BI2rAht0C0KFlL5GZG8J+xijGm7fdqOtbffqDcbzWZHAU/g9KJJiClknLvxIK6aEYADzoOZJM+LKlBo3Ei5IMmesiZTlrX32blNr9eJs7BD4TDLsq3x+e0q9l0AUQYFOjK3RC0HmYfQIwpCJtMSzWGSNn74w59ewimEDodDLDta/iTCSNRYQu4FCnQMCrs7AToS7ke+rRWVa/s//KFnN5HD3XA4HI6yRTXzpRnsUH8SlYeOjfKNYoWJvOshdj+A86E59Z0PP31yC1GBGQ6FwxEWewd/bKYU7KI+ZUewQDG4wUsT1Ru2aydsBmYPTx4Nq+8/efrEh2JOIhwOhSPpkfodKEOMLUUYFOiQCC2UkXSo1+sNcB7MJHkesqnCqLs+R+/cP/3B5RvyRU/t4vuJRKIlp6tWhiJbSbYr4l4iaKgxD5MgA6IMCnQYba//5E9PqWCNJeReoECH18Zpkj29rCKlr81ms9mdnn/BleSgo043GbbgATeUNmiKequJYAGPG224/+3XqQ8xthRhUKDDU1tFd/Uu4P7Fz81wWVgxbXWhiadFJhHRbBOyWEm2K+Be4qkqCmrGSZ3Flf/9yv925X+78r9d+d+u/G9X/rcr/9uV/+3K/8Z//Md//Md//Md//Md//Md//PdS4b8AAFZQOCBcAgAAsEUAnQEqEAQsAT9xuNlltK8rpyAIApAuCWlu4XdhG0AJ7APfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99snIe+2TkPfbJyHvtk5D32ych77ZOQ99scAAA/v+tHgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA==}!}
厉害了
可以可以
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