jdk interview questions
Top jdk frequently asked interview questions
I'm new to Java development under Ubuntu. When I typed javac in the terminal, it prompted me to install OpenJDK and a bunch of other JDKs. I want to know if there is any difference between OpenJDK 7 and Oracle's JDK 7. Are they basically the same? Thanks.
Source: (StackOverflow)
I'm trying to re-install Oracle JDK 7 32 bit to 64 bit Ubuntu (previously 64 bit JDK was installed). JDK is currently present at /usr/lib/jvm/jdk1.7.0
. I invoke
sudo update-alternatives --remove "java" "/usr/lib/jvm/jdk1.7.0/bin/java"
sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0/bin/java" 1
And then:
/usr/lib/jvm/jdk1.7.0/bin$ java
bash: /usr/bin/java: No such file or directory
Why java can't be invoked?
Source: (StackOverflow)
I want to install Oracle's JRE and to update to the latest version with the Software Updater when they released. Is there a Ubuntu package that is provided by Canonical or Oracle?
Before release Java 7, I followed this way to install Java 6.
But it doesn't work for Java 7. There is no package sun-java7-xxx
. How can you install Java 7?
Source: (StackOverflow)
I am getting my new laptop going and went to install the latest oracle JDK 7u25. I followed the instructions on this site to do it.
Afterwards when I type java --version
in the terminal I get the error:
Error: Could not create the Java Virtual Machine
I tried reinstalling it via a different method but the error wont go away. I am running Ubuntu 12.04 64bit.
Source: (StackOverflow)
This question already has an answer here:
Most of the software is not thoroughly tested with Java 7 and I would like to install Oracle's JDK 6.0 on Ubuntu 11.10.
Could someone please provide me the instructions for the same?
Source: (StackOverflow)
four@twenty:~$ file /etc/alternatives/java /etc/alternatives/javac
/etc/alternatives/java:symbolic link to `/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java'
/etc/alternatives/javac:symbolic link to `/usr/lib/jvm/java-6-openjdk-amd64/bin/javac'
Forgive my noobishness but Im interpreting that as the runtime environment using Java 7 but the compiler using 6?
Is this right and if so how can I set it to use 7?
Thanks :)
Source: (StackOverflow)
I want to start toying around with java (eventually getting to the point where I can write basic little programs for android or web), but I've managed to have java messed up on my computer (from past experiments).
I'm not sure which version of java I have, and would like to know if there is a command to see the version of java that is installed and active. Also, which version works best? All this on 32bit Ubuntu 12.04
EDIT:
Ok, so it seems like I have both openjdk 6 and 7, with openjdk 7 in use. I want to use openjdk 7, so how do I uninstall openjdk 6? Is just via USC good enough or is there a command that should be run?
Source: (StackOverflow)
I have installed tomcat7
(using apt-get install
) and whenever I want to start tomcat7
it says :
* no JDK found - please set JAVA_HOME
I have set JAVA_HOME
in my bash.bashrc
and also in ~/.bashrc
and when I issue echo $JAVA_HOME
I clearly see that this variable is pointing to my jdk's root folder. Can someone help me with this please?
Thanks
Source: (StackOverflow)
I am a new user of Linux, it has been recommended to me by my friend.
He told me to install software called IntelliJ Idea IDE.
Well I have been following the tutorial. But now when I try to open "idea.sh", an error message pops-up:
'tools.jar' is not in IDEA classpath.
Please ensure JAVA_HOME points to JDK rather than JRE.
Please remember that I'm new to Ubuntu and I'm planning for a nice long stay once I get myself into it :)
Also I do not know if I am running a correct Java6 JDK.
When I do java -version
, this is what I get:
java version "1.6.0_23"
OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre10-0ubuntu5)
OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)
Thank You for reading this and I hope I will get a nice response.
Source: (StackOverflow)
I can't compile a default new project for Android 2.1 because(?) the JDK used by Android Studio is JDK 1.7 but it should be JDK 1.6.
To change it I go to File -> Project Structure and try to find the JDK 1.6 location.
But when I select its directory and press OK I get the following error:
Please choose a valid JDK directory
As you can see on the screenshoot I'm trying to set Java 6 OpenJDK 64-bits as the new JDK.
What can I do? Isn't Android Studio compatible with OpenJDK and should I use Oracle JDK instead?
Source: (StackOverflow)
Is there any scripts for downloading and installing IntelliJ with JavaJDK or OpenJDK?
I don't know how I did it before using Ubuntu 12.10 but I'm now on a fresh 13.04 install and I have been looking around for an all in one script, or some scripts I can cobble together
I have the two links detailed that I think will be handy, can anyone else add to this please?
How do I install Oracle Java JDK 7?
Install Oracle Java 7 in Ubuntu via PPA Repository
Update: I have now found you can install IntelliJ through the Ubuntu software centre, so although this was a nice learning exercise for me it's not really relevant any more. Thanks to everyone that contributed.
Source: (StackOverflow)
I have Ubuntu 12.04 amd64 installed on my machine, on the previous versions of Ubuntu it was deadly easy, now there is this command update-java-alternatives
with a really bad man page.
I just have my JDK unpacked on a mounted partition like /media/mydisk/jdk
, how i can force the use of that JDK instead of the one that comes in the Ubuntu repository?
What is the logic behind this update-java-alternatives
?
Source: (StackOverflow)