Ubuntu版本是16.04.5 LTS；
确认OpenJDK11源码已经下载到本地，下载方式可以参考文章《Ubuntu环境下载OpenJDK11源码》、《利用Docker极速下载OpenJDK11源码》；
安装OpenJDK10作为boot JDK，安装过程可以参考文章《Ubuntu下安装OpenJDK10》；
重要文件夹的位置
OpenJDK11源码解压后是个名为jdk11的文件夹，位于此目录下：/home/willzhao/work/compileopenjdk
OpenJDK10安装完成后，整体上是个名为jdk-10的文件夹，位于此目录下：/usr/lib/jvm，因此boot JDK的完整目录是/usr/lib/jvm/jdk-10
以上是我这边的文件路径，如果您和我的不一致也没关系，后面注意修改成您自己对应的即可；
正式开始
编译的时候会用到boot JDK的jre目录下的lib库，我们这里只有JDK没有jre，因此需要创建一个jre目录，再把jdk的lib文件夹复制到这个目录下，执行以下命令：
mkdir /usr/lib/jvm/jdk-10/jre && cp -r /usr/lib/jvm/jdk-10/lib /usr/lib/jvm/jdk-10/jre/
我用的是root账号，因此将OpenJDK11源码文件夹的所有者和用户组都改成root的，在目录/home/willzhao/work/compileopenjdk执行以下命令：
chown -R root jdk11 && chgrp -R root jdk11
安装必要的依赖应用：
apt-get install -y autoconf zip libx11-dev libxext-dev libxrender-dev libxtst-dev libxt-dev libcups2-dev libfontconfig1-dev libasound2-dev
进入OpenJDK11源码的目录/home/willzhao/work/compileopenjdk/jdk11
配置确认，这一步通过后就可以开始编译了：
bash configure --with-num-cores=4 --with-memory-size=8192
以上命令中—with-num-cores=4表示四核CPU参与编译，—with-memory-size=8192表示8G内存参与编译，请您根据自己电脑的实际配置来调整；
如果配置不通过会有相关提示，请按照提示内容做调整，步骤3中的安装的那些应用其实都是配置检查不通过时提示要安装的；
配置确认通过后，控制台提示信息大致如下：
====================================================
A new configuration has been successfully created in
/home/willzhao/work/compileopenjdk/jdk11/build/linux-x86_64-normal-server-release
using configure arguments '--with-num-cores=4 --with-memory-size=8192'.
Configuration summary:
* Debug level: release
* HS debug level: product
* JVM variants: server
* JVM features: server: 'aot cds cmsgc compiler1 compiler2 epsilongc g1gc graal jfr jni-check jvmci jvmti management nmt parallelgc serialgc services vm-structs'
* OpenJDK target: OS: linux, CPU architecture: x86, address length: 64
* Version string: 11-internal+0-adhoc.root.jdk11 (11-internal)
Tools summary:
* Boot JDK: openjdk version "10" 2018-03-20 OpenJDK Runtime Environment 18.3 (build 10+44) OpenJDK 64-Bit Server VM 18.3 (build 10+44, mixed mode) (at /usr/lib/jvm/jdk-10)
* Toolchain: gcc (GNU Compiler Collection)
* C Compiler: Version 5.4.0 (at /usr/bin/gcc)
* C++ Compiler: Version 5.4.0 (at /usr/bin/g++)
Build performance summary:
* Cores to use: 4
* Memory limit: 8192 MB
执行命令make即可开始编译，等待编译完成后控制台输出以下类似信息：
Creating support/modules_cmds/jdk.pack/pack200 from 1 file(s)
Creating support/modules_cmds/jdk.pack/unpack200 from 7 file(s)
Creating support/modules_cmds/jdk.rmic/rmic from 1 file(s)
Creating support/modules_cmds/jdk.scripting.nashorn.shell/jjs from 1 file(s)
Creating support/modules_libs/jdk.sctp/libsctp.so from 3 file(s)
Creating support/modules_libs/jdk.security.auth/libjaas.so from 1 file(s)
Compiling 4 files for BUILD_JIGSAW_TOOLS
Stopping sjavac server
Finished building target 'default (exploded-image)' in configuration 'linux-x86_64-normal-server-release'
打开jdk11/build/linux-x86_64-normal-server-release目录下的build.log文件可以看到更详细的日志：
Creating support/modules_cmds/jdk.pack/unpack200 from 7 file(s)
Creating support/modules_cmds/jdk.rmic/rmic from 1 file(s)
Creating support/modules_cmds/jdk.scripting.nashorn.shell/jjs from 1 file(s)
Creating support/modules_libs/jdk.sctp/libsctp.so from 3 file(s)
Creating support/modules_libs/jdk.security.auth/libjaas.so from 1 file(s)
Compiling 4 files for BUILD_JIGSAW_TOOLS
----- Build times -------
Start 2018-10-23 14:45:20
End 2018-10-23 14:53:53
00:08:33 TOTAL
-------------------------
Finished building target 'default (exploded-image)' in configuration 'linux-x86_64-normal-server-release'
在jdk11/build/linux-x86_64-normal-server-release目录下，有个jdk目录，这里面就是最新构建的OpenJDK，进入里面的bin目录，再执行命令./java -version，可见最新的版本信息如下，已经是11版本了：
root@willzhao-Lenovo-Ubuntu16:/home/willzhao/work/compileopenjdk/jdk11/build/linux-x86_64-normal-server-release/jdk/bin# ./java -version
openjdk version "11-internal" 2018-09-25
OpenJDK Runtime Environment (build 11-internal+0-adhoc.root.jdk11)
OpenJDK 64-Bit Server VM (build 11-internal+0-adhoc.root.jdk11, mixed mode)
至此，基于OpenJDK11源码编译构建已经成功，去/etc/profile文件中做好环境变量设置就能正常使用新的JDK了；