stackoverflow上Java相关回答整理翻译

「爱情、让人受尽委屈。」 2022-07-13 04:27 199阅读 0赞

原文链接：[https://github.com/giantray/stackoverflow-java-top-qa][https_github.com_giantray_stackoverflow-java-top-qa]

# stackoverflow-Java-top-qa #

对stackoverflow上Java相关、投票数TOP100的问答进行翻译，欢迎点star，我们会持续更新!!!
    
    为了让“翻译”更有意义，给阅读者带来更多、更有效的收获，我们会有一些加工：
    例如，对问题进行分类，整合多个答案、删除冗余内容、加上自己的验证结果、心得等等
    
    对于参与翻译的人，这也是很好的一个学习、理解过程，欢迎大家一起来翻译

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### 如何参与翻译（欢迎加入翻译组QQ群485011036） ###

#### 如何参与： ####

*  请从下文“待翻译问题链接”中寻找你感兴趣的问答进行翻译。翻译好的问答，放到contents目录下，无需更新readme.md文档。之后提一个PR，我负责合并PR并更新到readme中。
 *  另外，为了避免多人重复新翻译一个问题，你可以提issue，说明你计划翻译的问题及时间点，我可以先更新到下面的”未翻译问题“中，说明已有人领了这个问题。当然，也不一定要提issue，一般情况下，只要及时提pr，我及时审核，出现”撞车“的概率并不高。

#### 一些基本的约定： ####

*  文档的文件名，和stackoverflowhich-notnull-java-annotation-should-i-usew上的url保持一致。例如，[http://stackoverflow.com/questions/8710619/java-operator][http_stackoverflow.com_questions_8710619_java-operator] 的文件名， 就是java-operator.md
 *  在每篇翻译文档内容的最后，要附上stackoverflow的原文链接

#### 每个人可以做（但不限于）： ####

*  找未翻译的问题进行翻译
 *  优化已翻译的问题
 *  输出问答精简汇总版（把所有的问答集中到一个md文件，然后尽量精简，让别人可以在一天内把这100个问题的精髓都看完）
 *  输出gitbook版本（现在直接在github上查看，体验不好）

#### 文档优化反馈： ####

请大家多多反馈，优化已翻译好的文章：可以到[吐槽区][Link 1]吐槽，也可以在已翻译文章基础上进行优化，提新的PR。文章质量的提升，需要大家一起努力！

### 目录 ###

> 基础语法

*  [Java += 操作符实质][Java _]
 *  [将InputStream转换为String][InputStream_String]
 *  [将数组转换为List][List]
 *  [如何遍历map对象][map]
 *  [public，protected，private，不加修饰符。有什么区别呢？][public_protected_private]
 *  [如何测试一个数组是否包含指定的值？][Link 2]
 *  [重写（Override）equlas和hashCode方法时应考虑的问题][Override_equlas_hashCode]
 *  [从一个多层嵌套循环中直接跳出][Link 3]
 *  [如何将String转换为Int][String_Int]
 *  [如何分割（split）string字符串][split_string]
 *  [在java中如何对比（compare）string][java_compare_string]
 *  [`Map<Key,Value>`基于Value值排序][Map_Key_Value_Value]
 *  [\`HashMap和Hashtable的区别][HashMap_Hashtable]
 *  [如何便捷地将两个数组合到一起][Link 4]
 *  [Java 是否支持默认的参数值][Java]
 *  [Java 产生指定范围的随机数][Java 1]
 *  [JavaBean 到底是什么][JavaBean]
 *  [wait()和sleep()的区别][wait_sleep]
 *  [能否在一个构造器( `constructor` )中调用另一个构造器][_constructor_]
 *  [ `finally` 代码块总会被执行么][_finally_]
 *  [如何将String转换为enum][String_enum]
 *  [在Java中声明数组][Java 2]
 *  [反射是什么及其用途][Link 5]
 *  [为什么不能用string类型进行switch判断][string_switch]
 *  [比较java枚举成员使用equal还是==][java_equal]
 *  [用java怎么创建一个文件并向该文件写文本内容][java]
 *  [serialVersionUID 有什么作用？该如何使用？][serialVersionUID]
 *  [为什么Java的`Vector`类被认为是过时的或者废弃的][Java_Vector]
 *  [Java的foreach循环是如何工作的][Java_foreach]
 *  为什么相减这两个时间（1927年）会得到奇怪的结果
 *  Java 中如何将 String 转换为 enum
 *  该什么时候使用 ThreadLocal变量，它是如何工作的
 *  servlets的运行原理
 *  如何计算MD5值
 *  Java中软引用和弱引用的区别
 *  JSF, Servlet 和 JSP (三种技术)有什么区别
 *  Java内部类和嵌套静态类
 *  @Component, @Repository, @Service的区别
 *  如何创建泛型java数组

> 编程技巧

*  [去掉烦人的“!=null”(判空语句][null]
 *  [获取完整的堆栈信息][Link 6]
 *  [如何用一行代码初始化一个ArrayList][ArrayList]
 *  [初始化静态map][map 1]
 *  [给3个布尔变量，当其中有2个或者2个以上为true才返回true][3_2_2_true_true]
 *  [输出 Java 数组最简单的方式][Java 3]
 *  [为什么以下用随机生成的文字会得出 “hello world”?][_hello world]
 *  [什么在java中存放密码更倾向于char\[\]而不是String][java_char_String]
 *  [如何避免在JSP文件中使用Java代码][JSP_Java]
 *  [Java 源码里的设计模式][Java 4]
 *  [如何产生一个随机的字母数字串作为 session 的唯一标识符][session]
 *  [如何创建单例][Link 7]
 *  [实现Runnable接口 VS. 继承Thread类][Runnable_ VS. _Thread]
 *  [我应该用哪一个@NotNull注解][NotNull]
 *  [怎样将堆栈追踪信息转换为字符串][Link 8]
 *  [如何处理 java.lang.outOfMemoryError PermGen space error][java.lang.outOfMemoryError PermGen space error]
 *  [如何在整数左填充0][0]
 *  [在调用 instanceof 前需要进行null检查吗][instanceof _null]
 *  如何从文件里读取字符串
 *  遍历集合时移除元素，怎样避免ConcurrentModificationException异常抛出
 *  如何让IntelliJ编辑器永久性显示代码行数
 *  如何使用maven把项目及其依赖打包为可运行jar包

> 网络

*  [如何使用java.net.URLConnection接收及发送HTTP请求][java.net.URLConnection_HTTP]

> 性能

*  [LinkedList、ArrayList各自的使用场景，如何确认应该用哪一个呢？][LinkedList_ArrayList]
 *  [StringBuilder和StringBuffer有哪些区别呢][StringBuilder_StringBuffer]
 *  [为什么处理排序的数组要比非排序的快][Link 9]
 *  [如何使用Java创建一个内存泄漏的程序][Java 5]
 *  [为什么打印“B”会明显的比打印“\#”慢][B]

> 测试

*  [如何测试 private 方法，变量或者内部类][private]
 *  JUnit4如何断言确定异常的抛出

> Android

*  [在Android里面下载文件，并在ProgressDialog显示进度][Android_ProgressDialog]
 *  [如何获取Android设备唯一ID][Android_ID]
 *  安装Android SDK的时候找不到JDK

### 待翻译问题链接(还剩x问题) ###

*  [Proper use cases for Android UserManager.isUserAGoat()?][Proper use cases for Android UserManager.isUserAGoat]
 *  [Why is executing Java code in comments with certain Unicode characters allowed?][Why is executing Java code in comments with certain Unicode characters allowed]
 *  [Convert a String to an enum in Java][]
 *  [‘Must Override a Superclass Method’ Errors after importing a project into Eclipse][Must Override a Superclass Method_ Errors after importing a project into Eclipse]
 *  [Fastest way to determine if an integer’s square root is an integer][Fastest way to determine if an integer_s square root is an integer]
 *  [How to fix: Unsupported major.minor version 51.0 error?][How to fix_ Unsupported major.minor version 51.0 error]
 *  [How to generate a random alpha-numeric string?][How to generate a random alpha-numeric string]
 *  [Failed to load the JNI shared Library (JDK)][Failed to load the JNI shared Library _JDK]
 *  [What exactly is Apache Camel?][What exactly is Apache Camel]
 *  [Access restriction on class due to restriction on required library rt.jar?][Access restriction on class due to restriction on required library rt.jar]
 *  [How do I discover memory usage of my application in Android?][How do I discover memory usage of my application in Android]
 *  [Uncatchable ChuckNorrisException][]
 *  [Can I add jars to maven 2 build classpath without installing them?][Can I add jars to maven 2 build classpath without installing them]
 *  [Update Eclipse with Android development tools v. 23][]
 *  [Setting multiple jars in java classpath][]
 *  [What is the Java equivalent for LINQ?][What is the Java equivalent for LINQ]
 *  [Hibernate hbm2ddl.auto possible values and what they do?][Hibernate hbm2ddl.auto possible values and what they do]
 *  [How can I pad an integers with zeros on the left?][How can I pad an integers with zeros on the left]
 *  [Sort ArrayList of custom Objects by property][]
 *  [Efficiency of Java “Double Brace Initialization”?][Efficiency of Java _Double Brace Initialization]
 *  [Why does this go into an infinite loop?][Why does this go into an infinite loop]
 *  [decompiling DEX into Java sourcecode][]
 *  [Why does Math.round(0.49999999999999994) return 1][Why does Math.round_0.49999999999999994_ return 1]
 *  [Eclipse: Set maximum line length for auto formatting?][Eclipse_ Set maximum line length for auto formatting]
 *  [What is the equivalent of the C++ Pair][What is the equivalent of the C_ Pair]

### contributors ###

thx a lot:)

*  [giantray][]
 *  [wklken][]

more [link][]

--------------------

To Be Continue …

giantray

Email: lizeyang@foxmail.com

Blog: [http://blog.csdn.net/lizeyang][http_blog.csdn.net_lizeyang]

2015-08-18 于珠海

[https_github.com_giantray_stackoverflow-java-top-qa]: https://github.com/giantray/stackoverflow-java-top-qa
[http_stackoverflow.com_questions_8710619_java-operator]: http://stackoverflow.com/questions/8710619/java-operator
[Link 1]: https://github.com/giantray/stackoverflow-java-top-qa/issues/66
[Java _]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/java-operator.md
[InputStream_String]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/read-convert-an-inputstream-to-a-string.md
[List]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/create-arraylist-from-array.md
[map]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/iterate-through-a-hashmap.md
[public_protected_private]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/in-java-whats-the-difference-between-public-default-protected-and-private.md
[Link 2]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-test-if-an-array-contains-a-certain-value.md
[Override_equlas_hashCode]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-issues-should-be-considered-when-overriding-equals-and-hashcode-in-java.md
[Link 3]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/breaking-out-of-nested-loops-in-java.md
[String_Int]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/converting-string-to-int-in-java.md
[split_string]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-split-a-string-in-java.md
[java_compare_string]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-do-i-compare-strings-in-java.md
[Map_Key_Value_Value]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-sort-a-mapkey-value-on-the-values-in-java.md
[HashMap_Hashtable]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/differences-between-hashmap-and-hashtable.md
[Link 4]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-concatenate-two-arrays-in-java.md
[Java]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/does-java-support-default-parameter-values.md
[Java 1]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/generating-random-integers-in-a-range-with-Java.md
[JavaBean]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-a-javabean-exactly.md
[wait_sleep]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/difference-between-wait-and-sleep.md
[_constructor_]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-do-i-call-one-constructor-from-another-in-java.md
[_finally_]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/does-finally-always-execute-in-java.md
[String_enum]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/convert-a-string-to-an-enum-in-java.md
[Java 2]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/declare-array-in-java.md
[Link 5]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-reflection-and-why-is-it-useful.md
[string_switch]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-cant-i-switch-on-a-string.md
[java_equal]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/comparing-java-enum-members-or-equals.md
[java]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-create-a-file-and-write-to-a-file-in-java.md
[serialVersionUID]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-a-serialversionuid-and-why-should-i-use-it.md
[Java_Vector]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-java-vector-class-considered-obsolete-or-deprecated.md
[Java_foreach]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-does-the-java-for-each-loop-work.md
[null]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/avoiding-null-statements-in-java.md
[Link 6]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/get-current-stack-trace-in-java.md
[ArrayList]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/initialization-of-an-arraylist-in-one-line.md
[map 1]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-initialize-a-static-map.md
[3_2_2_true_true]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/check-if-at-least-two-out-of-three-booleans-are-true.md
[Java 3]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/whats-the-simplest-way-to-print-a-java-array.md
[_hello world]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-does-this-code-using-random-strings-print-hello-world.md
[java_char_String]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-char-preferred-over-string-for-passwords-in-java.md
[JSP_Java]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-avoid-java-code-in-jsp-files.md
[Java 4]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/examples-of-gof-design-patterns-in-javas-core-libraries.md
[session]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-generate-a-random-alpha-numeric-string.md
[Link 7]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-an-efficient-way-to-implement-a-singleton-in-java.md
[Runnable_ VS. _Thread]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/implements-runnable-vs-extends-thread.md
[NotNull]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/which-notnull-java-annotation-should-i-use.md
[Link 8]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-convert-a-stack-trace-to-a-string.md
[java.lang.outOfMemoryError PermGen space error]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/dealing-with-java-lang-outofmemoryerror-permgen-space-error.md
[0]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-pad-an-integers-with-zeros-on-the-left.md
[instanceof _null]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/is-null-check-needed-before-calling-instanceof.md
[java.net.URLConnection_HTTP]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/using-java-net-urlconnection-to-fire-and-handle-http-requests.md
[LinkedList_ArrayList]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/when-to-use-linkedlist-over-arraylist.md
[StringBuilder_StringBuffer]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/stringbuilder-and-stringbuffer.md
[Link 9]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-processing-a-sorted-array-faster-than-an-unsorted-array.md
[Java 5]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/creating-a-memory-leak-with-java.md
[B]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-printing-b-dramatically-slower-than-printing.md
[private]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-test-a-class-that-has-private-methods-fields-or-inner-classes.md
[Android_ProgressDialog]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/download-a-file-with-android-and-showing-the-progress-in-a-progressdialog.md
[Android_ID]: https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/is-there-a-unique-android-device-id.md
[Proper use cases for Android UserManager.isUserAGoat]: http://stackoverflow.com/questions/13375357/proper-use-cases-for-android-usermanager-isuseragoat
[Why is executing Java code in comments with certain Unicode characters allowed]: http://stackoverflow.com/questions/30727515/why-is-executing-java-code-in-comments-with-certain-unicode-characters-allowed
[Convert a String to an enum in Java]: http://stackoverflow.com/questions/604424/convert-a-string-to-an-enum-in-java
[Must Override a Superclass Method_ Errors after importing a project into Eclipse]: http://stackoverflow.com/questions/1678122/must-override-a-superclass-method-errors-after-importing-a-project-into-eclips
[Fastest way to determine if an integer_s square root is an integer]: http://stackoverflow.com/questions/295579/fastest-way-to-determine-if-an-integers-square-root-is-an-integer
[How to fix_ Unsupported major.minor version 51.0 error]: http://stackoverflow.com/questions/10382929/how-to-fix-unsupported-major-minor-version-51-0-error
[How to generate a random alpha-numeric string]: http://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string
[Failed to load the JNI shared Library _JDK]: http://stackoverflow.com/questions/7352493/failed-to-load-the-jni-shared-library-jdk
[What exactly is Apache Camel]: http://stackoverflow.com/questions/8845186/what-exactly-is-apache-camel
[Access restriction on class due to restriction on required library rt.jar]: http://stackoverflow.com/questions/860187/access-restriction-on-class-due-to-restriction-on-required-library-rt-jar
[How do I discover memory usage of my application in Android]: http://stackoverflow.com/questions/2298208/how-do-i-discover-memory-usage-of-my-application-in-android
[Uncatchable ChuckNorrisException]: http://stackoverflow.com/questions/13883166/uncatchable-chucknorrisexception
[Can I add jars to maven 2 build classpath without installing them]: http://stackoverflow.com/questions/364114/can-i-add-jars-to-maven-2-build-classpath-without-installing-them
[Update Eclipse with Android development tools v. 23]: http://stackoverflow.com/questions/24437564/update-eclipse-with-android-development-tools-v-23
[Setting multiple jars in java classpath]: http://stackoverflow.com/questions/219585/setting-multiple-jars-in-java-classpath
[What is the Java equivalent for LINQ]: http://stackoverflow.com/questions/1217228/what-is-the-java-equivalent-for-linq
[Hibernate hbm2ddl.auto possible values and what they do]: http://stackoverflow.com/questions/438146/hibernate-hbm2ddl-auto-possible-values-and-what-they-do
[How can I pad an integers with zeros on the left]: http://stackoverflow.com/questions/473282/how-can-i-pad-an-integers-with-zeros-on-the-left
[Sort ArrayList of custom Objects by property]: http://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property
[Efficiency of Java _Double Brace Initialization]: http://stackoverflow.com/questions/924285/efficiency-of-java-double-brace-initialization
[Why does this go into an infinite loop]: http://stackoverflow.com/questions/3831341/why-does-this-go-into-an-infinite-loop
[decompiling DEX into Java sourcecode]: http://stackoverflow.com/questions/1249973/decompiling-dex-into-java-sourcecode
[Why does Math.round_0.49999999999999994_ return 1]: http://stackoverflow.com/questions/9902968/why-does-math-round0-49999999999999994-return-1
[Eclipse_ Set maximum line length for auto formatting]: http://stackoverflow.com/questions/3697287/eclipse-set-maximum-line-length-for-auto-formatting
[What is the equivalent of the C_ Pair]: http://stackoverflow.com/questions/156275/what-is-the-equivalent-of-the-c-pairl-r-in-java
[giantray]: https://github.com/giantray
[wklken]: https://github.com/wklken
[link]: https://github.com/giantray/stackoverflow-java-top-qa/graphs/contributors
[http_blog.csdn.net_lizeyang]: http://blog.csdn.net/lizeyang