OpenJDK

I want to change maven java home which is open jdk with sun jdk. How can I do it ? root@ak-EasyNote-TM98:~# mvn -version Apache Maven 3.0.4 Maven home: /usr/share/maven Java version: 1.6.0_24, vendor: Sun Microsystems Inc. Java home: /usr/lib/jvm/java-6-openjdk-amd64/jre Default locale: tr_TR, platform encoding: UTF-8 OS name: "linux", version: "3.2.0-34-generic", arch: "amd64", family: "unix" Edit: So sorry. I forgot to write the below code : root@ak-EasyNote-TM98:~$ java -version java version "1.7.0_07" Java(TM) SE Runtime Environment (build 1.7.0_07-b10) Java HotSpot(TM) 64-Bit Server VM

序 本文主要研究一下openjdk的jvm.cfg文件 jdk8 /Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home/jre/lib/jvm.cfg # List of JVMs that can be used as an option to java, javac, etc. # Order is important -- first in this list is the default JVM. # NOTE that this both this file and its format are UNSUPPORTED and # WILL GO AWAY in a future release. # # You may also select a JVM in an arbitrary location with the # "-XXaltjvm=<jvm_dir>" option, but that too is unsupported # and may not be available in a future release. # -server KNOWN -client IGNORE 对于jdk8该文件在JAVA_HOME/jre/lib/目录下；其注释显示该配置文件用于配置java

Is it possible to browse the source code of OpenJDK online, just like I can do with SourceForge's projects? I never used Mercury before, so I felt confused. (Note: I don't want to download the source. I just want to browse it online, to see how some methods are implemented.) Use http://hg.openjdk.java.net/ as duncan suggested. The Mercurial interface there is quite confusing if you are not used to it, and since this is a large project, it can be hard to find what you are looking for. Here is an example: To find the JDK6 implementation java.util.List, select "jdk6", "jdk", select browse. Then

The OpenJDK code for java.util.HashMap includes the following line: static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16 Why is 1 << 4 used here, and not 16 ? I'm curious. It's to emphasize that the number is a power of two, and not a completely arbitrary choice. It thus alerts developers experimenting with different numbers that they should use other numbers in the pattern (e.g., 1 << 3 or 1 << 5 , rather than 20 ) so they don't break the methods which rely on the power of two requirement. There is a comment just above : /** * The default initial capacity - MUST be a power of two. */

概述   虽然JDK9.0已经出来了，不过我们系统最近才开始全面引入JDK1.8，JDK1.8也已经出来了好久了，各方面都挺稳定的。最近在使用lambda表达式的Collectors.toMap方法时就遇到了一个问题。 大致源码如下： public class Test { public static void main(String[] args) { // initMemberList为获取数据的方法 List<Member> list = Test.initMemberList(); Map<String, String> memberMap = list.stream().collect(Collectors.toMap(Member::getId, Member::getImgPath)); System.out.println(memberMap); } } class Member { private String id; private String imgPath; // get set省略 } 运行程序，直接提示： Exception in thread "main" java.lang.NullPointerException at java.util.HashMap.merge(HashMap.java:1224) at java.util.stream

概述   虽然JDK9.0已经出来了，不过我们系统最近才开始全面引入JDK1.8，JDK1.8也已经出来了好久了，各方面都挺稳定的。最近在使用lambda表达式的Collectors.toMap方法时就遇到了一个问题。 大致源码如下： public class Test { public static void main(String[] args) { // initMemberList为获取数据的方法 List<Member> list = Test.initMemberList(); Map<String, String> memberMap = list.stream().collect(Collectors.toMap(Member::getId, Member::getImgPath)); System.out.println(memberMap); } } class Member { private String id; private String imgPath; // get set省略 } 运行程序，直接提示： Exception in thread "main" java.lang.NullPointerException at java.util.HashMap.merge(HashMap.java:1224) at java.util.stream