Java“此语言级别不支持lambda表达式”
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Java "lambda expressions not supported at this language level"
提问by Czipperz
I was testing out some new features of Java 8 and copied the example into my IDE (Eclipse originally, then IntelliJ) as shown here
我的Java 8的一些新功能和复制的例子测试伸到我的IDE（Eclipse的原话的IntelliJ）如图所示这里
Eclipse offered no support whatsoever for lambda expressions, and IntelliJ kept reporting an error
Eclipse 不提供对 lambda 表达式的任何支持，并且 IntelliJ 不断报告错误
Lambda expressions not supported at this language level
此语言级别不支持 Lambda 表达式
I would like to know if this is a problem with my install, the code, or support.
我想知道这是否是我的安装、代码或支持方面的问题。
采纳答案by Abhilash Divakaran
In IntelliJ IDEA:
在 IntelliJ IDEA 中：
In File Menu→ Project Structure→ Project, change Project Language Levelto 8.0 - Lambdas, type annotations etc.
在File Menu→ Project Structure→ 中Project，更改Project Language Level为8.0 - Lambdas, type annotations etc.
For Android 3.0+ Go File→ Project Structure→ Module→ appand In Properties Tab set Source Compatibilityand Target Compatibilityto 1.8 (Java 8)
对于 Android 3.0+ 转到File→ Project Structure→ Module→app并在属性选项卡中设置Source Compatibility并Target Compatibility转到1.8 (Java 8)
Screenshot:
截屏：
回答by Stephen C
Actually, Eclipse support for Java 8 is available: see hereand here.
实际上，Eclipse 对 Java 8 的支持是可用的：请参阅此处和此处。
- For Kepler, it is available as a "feature patch" against SR2 (i.e. Eclipse 4.3.2)
- For Luna (Eclipse 4.4) it will be in the standard release. (release schedule)
- 对于 Kepler，它可以作为针对 SR2（即 Eclipse 4.3.2）的“特性补丁”
- 对于 Luna (Eclipse 4.4)，它将在标准版本中。（发布时间表）
回答by Gijs Overvliet
As Stephen C pointed out, Eclipse Kepler (4.3) has Java 8 support when the patch is installed (installation instructions here)
正如 Stephen C 指出的，Eclipse Kepler (4.3) 在安装补丁时支持 Java 8（安装说明在这里）
Once installed, you'll need to tell your projects to use java 8. First add the JDK to eclipse:
安装后，您需要告诉您的项目使用 java 8。首先将 JDK 添加到 eclipse：
- Go to Window -> Preferences
- Go to Java -> Installed JREs
- Add Standard VM, and point to the location of the JRE
- Then go to Compiler
- Set Compiler compliance level to 1.8
- 转到窗口 -> 首选项
- 转到 Java -> 已安装的 JRE
- 添加标准VM，并指向JRE的位置
- 然后进入编译器
- 将编译器合规性级别设置为 1.8
Then tell the project to use JDK 1.8:
然后告诉项目使用JDK 1.8：
- Go to Project -> preferences
- Go to Java Compiler
- Enable project specific settings
- Set Compiler compliance level to 1.8
- 转到项目 -> 首选项
- 转到 Java 编译器
- 启用项目特定设置
- 将编译器合规性级别设置为 1.8
回答by prayagupd
For intellij 13,
Simply change the Project language levelitself to 8.0with following navigation.
对于 Intellij 13，只需使用以下导航将项目语言级别本身更改为8.0。
File
|
|
---------Project Structure -> Project tab
|
|________Project language level
Module lang level
模块语言级别
I also had to update Modules lang levelwhen there was no maven plugin for java compiler.
Modules lang level当没有 .maven 插件时，我也不得不更新java compiler。
File
|
|
---------Project Structure -> Modules tab
|
|________ language level
But this Module lang levelwould automatically be fixed if there's already a maven pluginfor it,
但是Module lang level如果已经有一个maven plugin，这将自动修复，
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
After changes everything looks good
更改后一切看起来都不错
回答by user2682809
You should change source code Language Level also on the Source tab (Modules part).
您还应该在源选项卡（模块部分）上更改源代码语言级别。
回答by Daniel de Zwaan
To compile with Java 8 (lambdas etc) in IntelliJ IDEA 15;
在 IntelliJ IDEA 15 中使用 Java 8（lambdas 等）进行编译；
CTRL + ALT + SHIFT + Sor File / Project StructureOpen Project tab
Set Project SDK to compatible java version (1.8)
Set Project language level to 8
Open Modules tab
Set Language level to 8, click OK
CTRL + ALT + Sor File / SettingsBuild, Execution, Deployment / Compiler / Java Compiler
Change Target bytecode version to 1.8, click OK
CTRL + ALT + SHIFT + S或文件/项目结构打开项目选项卡
将项目 SDK 设置为兼容的 Java 版本 (1.8)
将项目语言级别设置为 8
打开模块选项卡
将语言级别设置为 8，单击“确定”
CTRL + ALT + S或文件/设置构建、执行、部署/编译器/Java编译器
将目标字节码版本更改为 1.8，单击确定
回答by user5760784
In intellij 14, following settings worked for me. Intellij14 Settings
在 Intellij 14 中，以下设置对我有用。 Intellij14 设置
回答by Dean Jain
Even after applying above defined project specific settings on IntelliJ as well as Eclipse, it was still failing for me !
即使在 IntelliJ 和 Eclipse 上应用了上面定义的项目特定设置后，它对我来说仍然失败！
what worked for me was addition of maven plugin with source and target with 1.8 setting in POM XML:
对我有用的是在POM XML中添加带有源和目标的maven插件，设置为1.8：
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.0.2</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>com.abc.sparkcore.JavaWordCount</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy</id>
<phase>install</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
回答by Toseef Zafar
回答by kuzevni
Possible Cause #1 (same as the first 3 answers for this question): Project Structure Settings
可能的原因 #1（与此问题的前 3 个答案相同）：项目结构设置
File > Project Structure > Under Project Settings, go to Project > set Project SDKto 1.8 (with version 65 or above, latest is 112) and set Project Language Levelto 8.
File > Project Structure > Under Platform Settings, go to Project > ensure that your JDK home pathis set to 1.8 (with version 65 or above, latest is 112).
文件>项目结构>在项目设置下，进入项目>将项目SDK设置为1.8（65或以上版本，最新为112）并将项目语言级别设置为8。
文件 > 项目结构 > 在平台设置下，进入项目 > 确保您的JDK 主路径设置为 1.8（65 或更高版本，最新为 112）。
If the above does not work, check the target bytecode versionof your compiler and move on to Possible Cause #2.
如果上述方法不起作用，请检查编译器的目标字节码版本，然后转到可能的原因 #2。
Possible Cause #2: Compiler
可能的原因#2：编译器
- File > Settings > Build, Execution, Deployment > Under Compiler, go to Java Compiler > set your Project Bytecode Versionto 1.8, as well as all the Target Bytecode Versionfor your modules. Click Applyand hit OK. Restart your IntelliJ IDE. Lambda expression was accepted in my IDE at this point.
- 文件 > 设置 > 构建、执行、部署 > 在编译器下，转到 Java 编译器 > 将您的项目字节码版本以及模块的所有目标字节码版本设置为 1.8 。单击“应用”并单击“确定”。重新启动 IntelliJ IDE。此时我的 IDE 接受了 Lambda 表达式。
Best wishes :)
最好的祝愿 ：）
