I have done a yum search java before installing anything to see if may have already. It comes back with the following:libreadline-java-javadoc.i686 : Javadoc for libreadline-javalibvirt-java-devel.noarch : Compressed Java source files for libvirt-javalibvirt-java-javadoc.noarch : Java documentation for libvirt-javalpg-java-compat.noarch : Compatibility Java runtime library for LPG 1.xpki-java-tools.noarch : Certificate System - PKI Java-Based Toolspki-java-tools-javadoc.noarch : Certificate System - PKI Java-Based Toolsppl-java-javadoc.i686 : Javadocs for ppl-javajava-1.5.0-gcj.i686 : JPackage runtime compatibility layer for GCJjava-1.5.0-gcj-devel.i686 : JPackage development compatibility layer for GCJjava-1.5.0-gcj-javadoc.i686 : API documentation for libgcjjava-1.5.0-gcj-src.i686 : Source files for libgcjjava-1.6.0-openjdk.i686 : OpenJDK Runtime Environmentjava-1.6.0-openjdk-demo.i686 : OpenJDK Demosjava-1.6.0-openjdk-devel.i686 : OpenJDK Development Environmentjava-1.6.0-openjdk-javadoc.i686 : OpenJDK API Documentationjava-1.6.0-openjdk-src.i686 : OpenJDK Source Bundlejava-1.7.0-openjdk.i686 : OpenJDK Runtime Environmentjava-1.7.0-openjdk-demo.i686 : OpenJDK Demosjava-1.7.0-openjdk-devel.i686 : OpenJDK Development Environmentjava-1.7.0-openjdk-javadoc.noarch : OpenJDK API Documentationjava-1.7.0-openjdk-src.i686 : OpenJDK Source BundleSo does this mean I have it installed or is this just some general information pertaining to what java can run on the system?
Unsure about java JDK for Centos 6.4
centos;java
In a simple answer, probably not.Running the command yum search java just shows you possible packages that match your search criteria. To see what's installed you need to search using either rpm or query using yum list installed Examplesrpm$ rpm -aq | grep -E jdk|javayum$ yum list installed java* jdk*Loaded plugins: auto-update-debuginfo, langpacks, refresh-packagekitInstalled Packagesjava-1.7.0-openjdk.x86_64                                                 1:1.7.0.60-2.4.3.0.fc19                                            @updates java-1.7.0-openjdk-devel.x86_64                                           1:1.7.0.60-2.4.3.0.fc19                                            @updates javahelp2.noarch                                                          2.0.05-13.fc19                                                     @fedora  javamail.noarch                                                           1.4.3-16.fc19                                                      @fedora  javapackages-tools.noarch                                                 0.15.0-2.fc19                                                      @updates jdk.x86_64                                                                2000:1.7.0_45-fcs                                                  installedSo in both outputs we can see that I have packages java and jdk installed. The reason I have 2 types of packages installed is because one is the Open JDK package. These are the RPM's named Java*. The version of Java distributed by Oracle/Sun are called JDK, these are the jdk* RPMs. This is the Java Developers Kit.You also might have the run-time environment installed (JRE), these are typically called jre*.