java关键词及其作用详解

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这个是自己平时学习java整理出来，其中包括关键字和保留字的详细解释，供大家参考和交流,高手勿嘲！
由于自己水平有限，整理中难免会有错误，若有错误请发邮件给我，我会及时更正。
E-mail:mothz@126.com

<html xmlns="http://www.w3.org/1999/xhtml"><meta charset="utf-8"><meta name="generator" content="pdf2htmlEX"><meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"><link rel="stylesheet" href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/base.min.css"><link rel="stylesheet" href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/fancy.min.css"><link rel="stylesheet" href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/raw.css"><script src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/js/compatibility.min.js"></script><script src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/js/pdf2htmlEX.min.js"></script><script>try{pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({});}catch(e){}</script><div id="sidebar" style="display: none"><div id="outline"></div></div><div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/bg1.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x1 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">Java 关键字及其作用</div><div class="t m0 x2 h4 y3 ff2 fs1 fc0 sc0 ls0 ws0">目录</div><div class="t m0 x3 h5 y4 ff1 fs2 fc0 sc0 ls0 ws0">JAVA 关键字及其作用............................................ ......................................................................... 1</div><div class="t m0 x4 h5 y5 ff2 fs2 fc0 sc0 ls0 ws0">一、 关键字总览:...............................................................................................................................2</div><div class="t m0 x4 h5 y6 ff2 fs2 fc0 sc0 ls0 ws0">二、 详细解释....................................................................................................................................3</div><div class="t m0 x5 h6 y7 ff4 fs2 fc0 sc0 ls0 ws0">1. </div><div class="t m1 x6 h7 y7 ff2 fs3 fc0 sc0 ls0 ws0">访问控制</div><div class="t m0 x7 h6 y7 ff4 fs2 fc0 sc0 ls0 ws0">.......................................................................................................................................3</div><div class="t m0 x6 h8 y8 ff3 fs4 fc0 sc0 ls0 ws0">1) private 私有的.........................................................................................................................................3</div><div class="t m0 x6 h8 y9 ff3 fs4 fc0 sc0 ls0 ws0">2) protected 受保护的................................................................................................................................3</div><div class="t m0 x6 h8 ya ff3 fs4 fc0 sc0 ls0 ws0">3) public 公共的..........................................................................................................................................3</div><div class="t m0 x5 h6 yb ff4 fs2 fc0 sc0 ls0 ws0">2. </div><div class="t m1 x6 h7 yb ff2 fs3 fc0 sc0 ls0 ws0">类、方法和变量修饰符</div><div class="t m0 x8 h6 yb ff4 fs2 fc0 sc0 ls0 ws0">...............................................................................................................4</div><div class="t m0 x6 h8 yc ff3 fs4 fc0 sc0 ls0 ws0">1) abstract 声明抽象...................................................................................................................................4</div><div class="t m0 x6 h8 yd ff3 fs4 fc0 sc0 ls0 ws0">2) class 类....................................................................................................................................................4</div><div class="t m0 x6 h8 ye ff3 fs4 fc0 sc0 ls0 ws0">3) extends 继承、扩展...............................................................................................................................4</div><div class="t m0 x6 h8 yf ff3 fs4 fc0 sc0 ls0 ws0">4) nal 最终、不可改变.............................................................................................................................4</div><div class="t m0 x6 h8 y10 ff3 fs4 fc0 sc0 ls0 ws0">5) implements 实现.....................................................................................................................................4</div><div class="t m0 x6 h8 y11 ff3 fs4 fc0 sc0 ls0 ws0">6) interface 接口..........................................................................................................................................5</div><div class="t m0 x6 h8 y12 ff3 fs4 fc0 sc0 ls0 ws0">7) nave 本地..............................................................................................................................................5</div><div class="t m0 x6 h8 y13 ff3 fs4 fc0 sc0 ls0 ws0">8) new 新,创建............................................................................................................................................5</div><div class="t m0 x6 h8 y14 ff3 fs4 fc0 sc0 ls0 ws0">9) stac 静态...............................................................................................................................................5</div><div class="t m0 x6 h8 y15 ff3 fs4 fc0 sc0 ls0 ws0">10) stric%p 严格,精准..................................................................................................................................5</div><div class="t m0 x6 h8 y16 ff3 fs4 fc0 sc0 ls0 ws0">11) synchronized 线程、同步.....................................................................................................................6</div><div class="t m0 x6 h8 y17 ff3 fs4 fc0 sc0 ls0 ws0">12) transient 短暂.......................................................................................................................................6</div><div class="t m0 x6 h8 y18 ff3 fs4 fc0 sc0 ls0 ws0">13) volale 易失..........................................................................................................................................6</div><div class="t m0 x5 h6 y19 ff4 fs2 fc0 sc0 ls0 ws0">3. </div><div class="t m1 x6 h7 y19 ff2 fs3 fc0 sc0 ls0 ws0">程序控制语句</div><div class="t m0 x9 h6 y19 ff4 fs2 fc0 sc0 ls0 ws0">...............................................................................................................................6</div><div class="t m0 x6 h8 y1a ff3 fs4 fc0 sc0 ls0 ws0">1) break 跳出，中断...................................................................................................................................6</div><div class="t m0 x6 h8 y1b ff3 fs4 fc0 sc0 ls0 ws0">2) connue 继续..........................................................................................................................................7</div><div class="t m0 x6 h8 y1c ff3 fs4 fc0 sc0 ls0 ws0">3) return 返回.............................................................................................................................................. 7</div><div class="t m0 x6 h8 y1d ff3 fs4 fc0 sc0 ls0 ws0">4) do 运行....................................................................................................................................................7</div><div class="t m0 x6 h8 y1e ff3 fs4 fc0 sc0 ls0 ws0">5) while 循环...............................................................................................................................................7</div><div class="t m0 x6 h8 y1f ff3 fs4 fc0 sc0 ls0 ws0">6) if 如果...................................................................................................................................................... 7</div><div class="t m0 x6 h8 y20 ff3 fs4 fc0 sc0 ls0 ws0">7) else 否则................................................................................................................................................. 7</div><div class="t m0 x6 h8 y21 ff3 fs4 fc0 sc0 ls0 ws0">8) for 循环................................................................................................................................................... 8</div><div class="t m0 x6 h8 y22 ff3 fs4 fc0 sc0 ls0 ws0">9) instanceof 实例.......................................................................................................................................8</div><div class="t m0 x6 h8 y23 ff3 fs4 fc0 sc0 ls0 ws0">10) switch 观察...........................................................................................................................................8</div><div class="t m0 x6 h8 y24 ff3 fs4 fc0 sc0 ls0 ws0">11) case 返回观察里的结果.......................................................................................................................8</div><div class="t m0 x6 h8 y25 ff3 fs4 fc0 sc0 ls0 ws0">12) default 默认..........................................................................................................................................8</div><div class="t m0 x5 h6 y26 ff4 fs2 fc0 sc0 ls0 ws0">4. </div><div class="t m1 x6 h7 y26 ff2 fs3 fc0 sc0 ls0 ws0">错误处理</div><div class="t m0 x7 h6 y26 ff4 fs2 fc0 sc0 ls0 ws0">.......................................................................................................................................9</div><div class="t m0 xa h9 y27 ff3 fs4 fc0 sc0 ls0 ws0">1</div></div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div></html><div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/bg2.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x6 h8 y28 ff3 fs4 fc0 sc0 ls0 ws0">1) try 捕获异常........................................................................................................................................... 9</div><div class="t m0 x6 h8 y29 ff3 fs4 fc0 sc0 ls0 ws0">2) catch 处理异常....................................................................................................................................... 9</div><div class="t m0 x6 h8 y2a ff3 fs4 fc0 sc0 ls0 ws0">3) throw 抛出一个异常对象.......................................................................................................................9</div><div class="t m0 x6 h8 y2b ff3 fs4 fc0 sc0 ls0 ws0">4) throws 声明一个异常可能被抛出.........................................................................................................9</div><div class="t m0 x5 h6 y2c ff4 fs2 fc0 sc0 ls0 ws0">5. </div><div class="t m1 x6 h7 y2c ff2 fs3 fc0 sc0 ls0 ws0">包相关</div><div class="t m0 xb h6 y2c ff4 fs2 fc0 sc0 ls0 ws0">.........................................................................................................................................10</div><div class="t m0 x6 h8 y2d ff3 fs4 fc0 sc0 ls0 ws0">1) import 引入...........................................................................................................................................10</div><div class="t m0 x6 h8 y2e ff3 fs4 fc0 sc0 ls0 ws0">2) package 包............................................................................................................................................. 10</div><div class="t m0 x5 h6 y2f ff4 fs2 fc0 sc0 ls0 ws0">6. </div><div class="t m1 x6 h7 y2f ff2 fs3 fc0 sc0 ls0 ws0">基本类型</div><div class="t m0 x7 h6 y2f ff4 fs2 fc0 sc0 ls0 ws0">.....................................................................................................................................10</div><div class="t m0 x6 h8 y30 ff3 fs4 fc0 sc0 ls0 ws0">1) boolean 布尔型.....................................................................................................................................10</div><div class="t m0 x6 h8 y31 ff3 fs4 fc0 sc0 ls0 ws0">2) byte 字节型...........................................................................................................................................10</div><div class="t m0 x6 h8 y32 ff3 fs4 fc0 sc0 ls0 ws0">3) char 字符型...........................................................................................................................................11</div><div class="t m0 x6 h8 y33 ff3 fs4 fc0 sc0 ls0 ws0">4) double 双精度.......................................................................................................................................11</div><div class="t m0 x6 h8 y34 ff3 fs4 fc0 sc0 ls0 ws0">5) +oat 浮点..............................................................................................................................................11</div><div class="t m0 x6 h8 y35 ff3 fs4 fc0 sc0 ls0 ws0">6) int 整型.................................................................................................................................................11</div><div class="t m0 x6 h8 y36 ff3 fs4 fc0 sc0 ls0 ws0">7) long 长整型...........................................................................................................................................12</div><div class="t m0 x6 h8 y37 ff3 fs4 fc0 sc0 ls0 ws0">8) short 短整型......................................................................................................................................... 12</div><div class="t m0 x6 h8 y38 ff3 fs4 fc0 sc0 ls0 ws0">9) null 空....................................................................................................................................................12</div><div class="t m0 x6 h8 y39 ff3 fs4 fc0 sc0 ls0 ws0">10) true 真.................................................................................................................................................12</div><div class="t m0 x6 h8 y3a ff3 fs4 fc0 sc0 ls0 ws0">11) false 假................................................................................................................................................12</div><div class="t m0 x5 h6 y3b ff4 fs2 fc0 sc0 ls0 ws0">7. </div><div class="t m1 x6 h7 y3b ff2 fs3 fc0 sc0 ls0 ws0">变量引用</div><div class="t m0 x7 h6 y3b ff4 fs2 fc0 sc0 ls0 ws0">.....................................................................................................................................13</div><div class="t m0 x6 h8 y3c ff3 fs4 fc0 sc0 ls0 ws0">1) super 父类,超类....................................................................................................................................13</div><div class="t m0 x6 h8 y3d ff3 fs4 fc0 sc0 ls0 ws0">2) this 本类................................................................................................................................................ 13</div><div class="t m0 x6 h8 y3e ff3 fs4 fc0 sc0 ls0 ws0">3) void 无返回值.......................................................................................................................................13</div><div class="t m0 x5 h6 y3f ff4 fs2 fc0 sc0 ls0 ws0">8. </div><div class="t m1 x6 h7 y3f ff2 fs3 fc0 sc0 ls0 ws0">保留字</div><div class="t m0 xb h6 y3f ff4 fs2 fc0 sc0 ls0 ws0">.........................................................................................................................................13</div><div class="t m0 x6 h8 y40 ff3 fs4 fc0 sc0 ls0 ws0">1) goto 跳转..............................................................................................................................................13</div><div class="t m0 x6 h9 y41 ff3 fs4 fc0 sc0 ls0 ws0">2) const </div><div class="t m1 xc ha y41 ff2 fs5 fc0 sc0 ls0 ws0">静态</div><div class="t m0 xd h9 y41 ff3 fs4 fc0 sc0 ls0 ws0">.............................................................................................................................................13</div><div class="t m0 x4 h5 y42 ff2 fs2 fc0 sc0 ls0 ws0">三、 文档说明:.................................................................................................................................14</div><div class="t m0 x3 hb y43 ff2 fs6 fc0 sc1 ls0 ws0">一、 关键字总览:</div><div class="t m0 xe hc y44 ff2 fs7 fc0 sc0 ls0 ws0">访问控制</div><div class="t m0 xf hd y45 ff3 fs7 fc1 sc0 ls0 ws0">private protected public</div><div class="t m0 x10 hc y46 ff2 fs7 fc0 sc0 ls0 ws0">类,方法和</div><div class="t m0 xe hc y47 ff2 fs7 fc0 sc0 ls0 ws0">变量修饰</div><div class="t m0 x11 hc y48 ff2 fs7 fc0 sc0 ls0 ws0">符</div><div class="t m0 x12 hd y49 ff3 fs7 fc1 sc0 ls0 ws0">abstract class extends nal implements interface nave new stac</div><div class="t m0 xf hd y4a ff3 fs7 fc1 sc0 ls0 ws0">stric%p synchronized transient volale</div><div class="t m0 xe hc y4b ff2 fs7 fc0 sc0 ls0 ws0">程序控制</div><div class="t m0 x13 hd y4c ff3 fs7 fc1 sc0 ls0 ws0">break connue return do while if else for instanceof</div><div class="t m0 x14 hd y4d ff3 fs7 fc1 sc0 ls0 ws0">switch case default</div><div class="t m0 xe hc y4e ff2 fs7 fc0 sc0 ls0 ws0">错误处理</div><div class="t m0 xc hd y4f ff3 fs7 fc1 sc0 ls0 ws0">try cathc throw throws</div><div class="t m0 x15 hc y50 ff2 fs7 fc0 sc0 ls0 ws0">包相关</div><div class="t m0 xf hd y51 ff3 fs7 fc1 sc0 ls0 ws0">import package</div><div class="t m0 xe hc y52 ff2 fs7 fc0 sc0 ls0 ws0">基本类型</div><div class="t m0 x12 hd y53 ff3 fs7 fc1 sc0 ls0 ws0">boolean byte char double +oat int long short null</div><div class="t m0 xb hd y54 ff3 fs7 fc1 sc0 ls0 ws0">true false</div><div class="t m0 xa h9 y27 ff3 fs4 fc0 sc0 ls0 ws0">2</div></div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a 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class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div><div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/bg3.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 xe hc y55 ff2 fs7 fc0 sc0 ls0 ws0">变量引用</div><div class="t m0 x13 hd y56 ff3 fs7 fc1 sc0 ls0 ws0">super this void</div><div class="t m0 x15 hc y57 ff2 fs7 fc0 sc0 ls0 ws0">保留字</div><div class="t m0 x16 hd y58 ff3 fs7 fc1 sc0 ls0 ws0">goto const</div><div class="t m0 x3 hb y59 ff2 fs6 fc0 sc1 ls0 ws0">二、 详细解释</div><div class="t m0 x17 hb y5a ff1 fs6 fc0 sc0 ls0 ws0">1. 访问控制</div><div class="t m0 x3 he y5b ff5 fs8 fc0 sc0 ls0 ws0">1) private </div><div class="t m1 x18 hf y5b ff2 fs9 fc2 sc2 ls0 ws0">私有的</div><div class="t m0 x18 he y5b ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y38 ff3 fs2 fc0 sc0 ls0 ws0">private 关键字是访问控制修饰符，可以应用于类、方法或字段（在类中声明的变量）。 只</div><div class="t m0 x5 h5 y39 ff2 fs2 fc0 sc0 ls0 ws0">能在声明 private（内部）类、方法或字段的类中引用这些类、方法或字段。在类的外部或</div><div class="t m0 x5 h5 y3a ff2 fs2 fc0 sc0 ls0 ws0">者对于子类而言，它们是不可见的。 所有类成员的默认访问范围都是 package 访问，也就</div><div class="t m0 x5 h5 y5c ff2 fs2 fc0 sc0 ls0 ws0">是说，除非存在特定的访问控制修饰符，否则，可以从同一个包中的任何类访问类成员。</div><div class="t m0 x3 he y5d ff5 fs8 fc0 sc0 ls0 ws0">2) protected </div><div class="t m1 x7 hf y5d ff2 fs9 fc2 sc2 ls0 ws0">受保护的</div><div class="t m0 x7 he y5d ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y5e ff3 fs2 fc0 sc0 ls0 ws0">protected 关键字是可以应用于类、方法或字段（在类中声明的变量）的访问控制修饰符。</div><div class="t m0 x5 h5 y5f ff2 fs2 fc0 sc0 ls0 ws0">可以在声明 protected 类、方法或字段的类、同一个包中的其他任何类以及任何子类（无论</div><div class="t m0 x5 h5 y60 ff2 fs2 fc0 sc0 ls0 ws0">子类是在哪个包中声明的）中引用这些类、方法或字段。所有类成员的默认访问范围都是</div><div class="t m0 x5 h5 y61 ff3 fs2 fc0 sc0 ls0 ws0">package 访问，也就是说，除非存在特定的访问控制修饰符，否则，可以从同一个包中的</div><div class="t m0 x5 h5 y62 ff2 fs2 fc0 sc0 ls0 ws0">任何类访问类成员。</div><div class="t m0 x3 he y63 ff5 fs8 fc0 sc0 ls0 ws0">3) public </div><div class="t m1 x12 hf y63 ff2 fs9 fc2 sc2 ls0 ws0">公共的</div><div class="t m0 x12 he y63 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y64 ff3 fs2 fc0 sc0 ls0 ws0">public 关键字是可以应用于类、方法或字段（在类中声明的变量）的访问控制修饰符。 可</div><div class="t m0 x5 h5 y65 ff2 fs2 fc0 sc0 ls0 ws0">能只会在其他任何类或包中引用 public 类、方法或字段。所有类成员的默认访问范围都是</div><div class="t m0 x5 h5 y66 ff3 fs2 fc0 sc0 ls0 ws0">package 访问，也就是说，除非存在特定的访问控制修饰符，否则，可以从同一个包中的</div><div class="t m0 x5 h5 y67 ff2 fs2 fc0 sc0 ls0 ws0">任何类访问类成员。</div><div class="t m0 xa h9 y27 ff3 fs4 fc0 sc0 ls0 ws0">3</div></div><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a><a class="l"><div class="d m2"></div></a></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div><div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/bg4.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x19 hb y68 ff1 fs6 fc0 sc0 ls0 ws0">2. 类、方法和变量修饰符</div><div class="t m0 x3 he y69 ff5 fs8 fc0 sc0 ls0 ws0">1) abstract </div><div class="t m1 x1a hf y69 ff2 fs9 fc2 sc2 ls0 ws0">声明抽象</div><div class="t m0 x1a he y69 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y6a ff3 fs2 fc0 sc0 ls0 ws0">abstract 关键字可以修改类或方法。abstract 类可以扩展（增加子类），但不能直接实例化。</div><div class="t m0 x5 h5 y6b ff3 fs2 fc0 sc0 ls0 ws0">abstract 方法不在声明它的类中实现，但必须在某个子类中重写。采用 abstract 方法的类本</div><div class="t m0 x5 h5 y6c ff2 fs2 fc0 sc0 ls0 ws0">来就是抽象类，并且必须声明为 abstract。</div><div class="t m0 x3 he y6d ff5 fs8 fc0 sc0 ls0 ws0">2) class </div></div><div class="c x1b y6e w3 h10"><div class="t m0 x0 he y6f ff6 fs8 fc2 sc0 ls0 ws0"> </div></div><div class="c x0 y1 w2 h2"><div class="t m1 x1c hf y6d ff2 fs9 fc2 sc2 ls0 ws0">类</div><div class="t m0 x1c he y6d ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y70 ff3 fs2 fc0 sc0 ls0 ws0">class 关键字用来声明新的 Java 类，该类是相关变量和/或方法的集合。类是面向对象的程</div><div class="t m0 x5 h5 y71 ff2 fs2 fc0 sc0 ls0 ws0">序设计方法的基本构造单位。类通常代表某种实际实体，如几何形状或人。类是对象的模</div><div class="t m0 x5 h5 y72 ff2 fs2 fc0 sc0 ls0 ws0">板。每个对象都是类的一个实例。要使用类，通常使用 new 操作符将类的对象实例化，然</div><div class="t m0 x5 h5 y73 ff2 fs2 fc0 sc0 ls0 ws0">后调用类的方法来访问类的功能。</div><div class="t m0 x3 he y74 ff5 fs8 fc0 sc0 ls0 ws0">3) extends </div><div class="t m1 xb hf y74 ff2 fs9 fc2 sc2 ls0 ws0">继承、扩展</div><div class="t m0 xb he y74 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y75 ff3 fs2 fc0 sc0 ls0 ws0">extends 关键字用在 class 或 interface 声明中，用于指示所声明的类或接口是其名称后跟有</div><div class="t m0 x5 h5 y76 ff3 fs2 fc0 sc0 ls0 ws0">extends 关键字的类或接口的子类。子类继承父类的所有 public 和 protected 变量和方法。</div><div class="t m0 x5 h5 y77 ff2 fs2 fc0 sc0 ls0 ws0">子类可以重写父类的任何非 nal 方法。一个类只能扩展一个其他类。</div><div class="t m0 x3 he y78 ff5 fs8 fc0 sc0 ls0 ws0">4) final </div><div class="t m1 x1d hf y78 ff2 fs9 fc2 sc2 ls0 ws0">最终、不可改变</div><div class="t m0 x1d he y78 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y79 ff3 fs2 fc0 sc0 ls0 ws0">nal 关键字可以应用于类，以指示不能扩展该类（不能有子类）。nal 关键字可以应用于</div><div class="t m0 x5 h5 y7a ff2 fs2 fc0 sc0 ls0 ws0">方法，以指示在子类中不能重写此方法。一个类不能同时是 abstract 又是 nal。abstract 意</div><div class="t m0 x5 h5 y7b ff2 fs2 fc0 sc0 ls0 ws0">味 着 必 须 扩 展 类 ， nal 意 味 着 不 能 扩 展 类 。 一 个 方 法 不 能 同 时 是 abstract 又 是</div><div class="t m0 x5 h5 y7c ff3 fs2 fc0 sc0 ls0 ws0">nal。abstract 意味着必须重写方法，nal 意味着不能重写方法。</div><div class="t m0 x3 he y7d ff5 fs8 fc0 sc0 ls0 ws0">5) implements </div></div><div class="c x1e y7e w3 h10"><div class="t m0 x0 he y7f ff6 fs8 fc2 sc0 ls0 ws0"> </div></div><div class="c x0 y1 w2 h2"><div class="t m1 x1f hf y7d ff2 fs9 fc2 sc2 ls0 ws0">实现</div><div class="t m0 x1f he y7d ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y80 ff3 fs2 fc0 sc0 ls0 ws0">implements 关键字在 class 声明中使用，以指示所声明的类提供了在 implements 关键字后</div><div class="t m0 x5 h5 y81 ff2 fs2 fc0 sc0 ls0 ws0">面的名称所指定的接口中所声明的所有方法的实现。类必须提供在接口中所声明的所有方</div><div class="t m0 x5 h5 y82 ff2 fs2 fc0 sc0 ls0 ws0">法的实现。一个类可以实现多个接口。</div><div class="t m0 xa h9 y27 ff3 fs4 fc0 sc0 ls0 ws0">4</div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div><div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/352760/bg5.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x3 he y83 ff5 fs8 fc0 sc0 ls0 ws0">6) interface </div><div class="t m1 x20 hf y83 ff2 fs9 fc2 sc2 ls0 ws0">接口</div><div class="t m0 x20 he y83 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x21 h5 y84 ff3 fs2 fc0 sc0 ls0 ws0">interface 关键字用来声明新的 Java 接口，接口是方法的集合。</div><div class="t m0 x21 h5 y85 ff2 fs2 fc0 sc0 ls0 ws0">接口是 Java 语言的一项强大功能。任何类都可声明它实现一个或多个接口，这意味着</div><div class="t m0 x5 h5 y86 ff2 fs2 fc0 sc0 ls0 ws0">它实现了在这些接口中所定义的所有方法。 </div><div class="t m0 x21 h5 y87 ff2 fs2 fc0 sc0 ls0 ws0">实现了接口的任何类都必须提供在该接口中的所有方法的实现。一个类可以实现多个</div><div class="t m0 x5 h5 y88 ff2 fs2 fc0 sc0 ls0 ws0">接口。</div><div class="t m0 x3 he y89 ff5 fs8 fc0 sc0 ls0 ws0">7) native </div><div class="t m1 x12 hf y89 ff2 fs9 fc2 sc2 ls0 ws0">本地</div><div class="t m0 x12 he y89 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y8a ff3 fs2 fc0 sc0 ls0 ws0">nave 关键字可以应用于方法，以指示该方法是用 Java 以外的语言实现的。</div><div class="t m0 x3 he y8b ff5 fs8 fc0 sc0 ls0 ws0">8) new </div><div class="t m1 x22 hf y8b ff2 fs9 fc2 sc2 ls0 ws0">新</div><div class="t m0 x22 he y8b ff6 fs8 fc2 sc0 ls0 ws0"> , </div><div class="t m1 x14 hf y8b ff2 fs9 fc2 sc2 ls0 ws0">创建</div><div class="t m0 x14 he y8b ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y8c ff3 fs2 fc0 sc0 ls0 ws0">new 关键字用于创建类的新实例。 </div><div class="t m0 x5 h11 y8d ff3 fs2 fc0 sc0 ls0 ws0">new 关键字后面的参数必须是类名，并且类名的后面必须是一组构造方法参数（必须带括</div><div class="t m0 x5 h11 y8e ff7 fs2 fc0 sc0 ls0 ws0">号）。 </div><div class="t m0 x5 h11 y8f ff2 fs2 fc0 sc0 ls0 ws0">参数集合必须与类的构造方法的签名匹配。 </div><div class="t m0 x5 h11 y90 ff3 fs2 fc0 sc0 ls0 ws0">= 左侧的变量的类型必须与要实例化的类或接口具有赋值兼容关系。</div><div class="t m0 x3 he y91 ff5 fs8 fc0 sc0 ls0 ws0">9) static </div><div class="t m1 x23 hf y91 ff2 fs9 fc2 sc2 ls0 ws0">静态</div><div class="t m0 x23 he y91 ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h11 y92 ff3 fs2 fc0 sc0 ls0 ws0">stac 关键字可以应用于内部类（在另一个类中定义的类）、方法或字段（类的成员变量）。</div><div class="t m0 x5 h12 y93 ff3 fs2 fc0 sc0 ls0 ws0"> </div><div class="t m0 x5 h5 y94 ff2 fs2 fc0 sc0 ls0 ws0">通常，stac 关键字意味着应用它的实体在声明该实体的类的任何特定实例外部可用。</div><div class="t m0 x5 h11 y95 ff3 fs2 fc0 sc0 ls0 ws0">stac（内部）类可以被其他类实例化和引用（即使它是顶级类）。在上面的示例中，另一</div><div class="t m0 x5 h11 y96 ff2 fs2 fc0 sc0 ls0 ws0">个类中的代码可以实例化 MyStacClass 类，方法是用包含它的类名来限定其名称，如</div><div class="t m0 x5 h5 y97 ff3 fs2 fc0 sc0 ls0 ws0">MyClass.MyStacClass。 </div><div class="t m0 x5 h11 y98 ff3 fs2 fc0 sc0 ls0 ws0">stac 字段（类的成员变量）在类的所有实例中只存在一次。 </div><div class="t m0 x5 h11 y99 ff2 fs2 fc0 sc0 ls0 ws0">可以从类的外部调用 stac 方法，而不用首先实例化该类。这样的引用始终包括类名作为</div><div class="t m0 x5 h11 y9a ff2 fs2 fc0 sc0 ls0 ws0">方法调用的限定符。</div><div class="t m0 x5 h11 y9b ff2 fs2 fc0 sc0 ls0 ws0">模式：public nal stac <type> varName = <value>; 通常用于声明可以在类的外部使用的类常</div><div class="t m0 x5 h11 y9c ff2 fs2 fc0 sc0 ls0 ws0">量。在引用这样的类常量时需要用类名加以限定。在上面的示例中，另一个类可以用</div><div class="t m0 x5 h11 y9d ff3 fs2 fc0 sc0 ls0 ws0">MyClass.MAX_OBJECTS 形式来引用 MAX_OBJECTS 常量。</div><div class="t m0 x3 he y9e ff5 fs8 fc0 sc0 ls0 ws0">10) strictfp </div><div class="t m1 x18 hf y9e ff2 fs9 fc2 sc2 ls0 ws0">严格</div><div class="t m0 x18 he y9e ff6 fs8 fc2 sc0 ls0 ws0"> , </div><div class="t m1 x24 hf y9e ff2 fs9 fc2 sc2 ls0 ws0">精准</div><div class="t m0 x24 he y9e ff6 fs8 fc2 sc0 ls0 ws0"> </div><div class="t m0 x5 h11 y9f ff3 fs2 fc0 sc0 ls0 ws0">stric%p 的意思是 FP-strict，也就是说精确浮点的意思。在 Java 虚拟机进行浮点运算时，如</div><div class="t m0 xa h9 y27 ff3 fs4 fc0 sc0 ls0 ws0">5</div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>