"which java" in CentOS prints wrong java path

Question

I am not sure why "which java" and "whereis java" paths are not correct. I tried to edit ~/.bash_profile and /etc/environment but did not help. The desired path is what is seen in "echo $JAVA_HOME" below but the same is not reflected in "which java"

Below is what I get in CentOS 6.4:

which java

/usr/bin/java

---

java -version

java version "1.7.0_45"

JAVA(TM) SE Runtime Environment (build 1.7.0_45-b18)

JAVA HotSpot (TM) 64-bit Server VM (build 24.45-b08, mixed mode)

---

whereis java

java: /usr/bin/java /etc/java /usr/lib/java /usr/share/java

---

echo $JAVA_HOME

/usr/java/jdk1.7.0_45/jre => desired shows correct when echo $JAVA_HOME

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Answer 1

Run alternatives --config java to pick the Java version you want to use as default. It will print out a list of installed Javas to choose from.

which java, however, will always print out /usr/bin/java. This doesn't mean it's set wrong! Observe:

$ ls -l `which java`
lrwxrwxrwx 1 root root 22 Oct 19 11:49 /usr/bin/java -> /etc/alternatives/java
$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 35 Oct 19 11:49 /etc/alternatives/java -> /usr/lib/jvm/jre-1.5.0-gcj/bin/java

If you use alternatives to change the path to IcedTea, ls -l /etc/alternatives/java will reflect that.

Answer 2

Your PATH (and nothing else) determines which directories to look for commands. This is the same in Linux, Solaris, and DOS.

When you do a which {command} it find the first directory you can execute the command in.

When you update your PATH in .bashrc, you have to source it again to change your current settings.

Answer 3

Sometimes alternatives does not work in a single command by selecting the desired version of java. I am not sure of the precise reason for this though..

I fell victim to such a scenario. The auto-pilot failed, we must fly manual now..

In any of below two files in your unix installation add following variables and a call to a shell script (I have provided below) -

~/.bashrc

export JAVA_HOME=/opt/jdk1.8.0_141
export PATH=$JAVA_HOME/bin:$PATH
sudo bash /appl/common/toFixJava.sh

OR

/etc/profile

export JAVA_HOME=/opt/jdk1.8.0_141
export PATH=$JAVA_HOME/bin:$PATH
sudo bash /appl/common/toFixJava.sh

The script below referenced above sets the rest of java modules to utilize the java you want to use -

toFixJava.sh

altrs="java javac jre jarsigner javadoc javafxpackager javah javap java-rmi.cgi javaws jcmd jconsole jcontrol jdb jhat jinfo jmap jmc jmc.ini jps jrunscript jsadebugd jstack jstat jstatd jvisualvm keytool appletviewer apt ControlPanel extcheck idlj native2ascii orbd pack200 policytool rmic rmid rmiregistry schemagen serialver servertool tnameserv unpack200 wsgen wsimport xjc"

for each in $altrs do

alternatives --install /usr/bin/$each $each /opt/jdk1.8.0_141/bin/$each <desired installation index number, e.g. 2>
alternatives --set $each /opt/jdk1.8.0_141/bin/$each

done

Please do let know if this doesn't work for you. I will help you solve alternatively!