404 Error - Jenkins not running but Tomcat is - jenkins

Question

I am new in this area. I see that the Tomcat service is running.
I verified that by entering URL http://localhost:8080.
But when I type http://localhost:8080/jenkins I get a 404 error.
I have verified the availability of <TOMCAT_HOME>/webapps/jenkins.war.
Does this mean I have to re-install both Tomcat and Jenkins? Or is there something more that I need to do?
UPDATED:
I downloaded jenkins.war version 1.658 from here - https://updates.jenkins-ci.org/download/war/ and replaced the old jenkins.war (version 1.568) with the relatively new one (version 1.658). I got the Error message with stacktrace when I tried http://localhost:8080/jenkins -
AWT is not properly configured on this server. Perhaps you need to run your container with "-Djava.awt.headless=true"? See also: https://wiki.jenkins-ci.org/display/JENKINS/Jenkins+got+java.awt.headless+problem
java.lang.UnsatisfiedLinkError: no freetype in java.library.path
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.loadLibrary0(Unknown Source)
at java.lang.System.loadLibrary(Unknown Source)
at sun.font.FontManagerNativeLibrary$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.font.FontManagerNativeLibrary.<clinit>(Unknown Source)
at sun.font.SunFontManager$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.font.SunFontManager.<clinit>(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at sun.font.FontManagerFactory$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.font.FontManagerFactory.getInstance(Unknown Source)
at java.awt.Font.getFont2D(Unknown Source)
at java.awt.Font.getFamily(Unknown Source)
at java.awt.Font.getFamily_NoClientCode(Unknown Source)
at java.awt.Font.getFamily(Unknown Source)
at java.awt.Font.toString(Unknown Source)
at hudson.util.ChartUtil.<clinit>(ChartUtil.java:255)
at hudson.WebAppMain.contextInitialized(WebAppMain.java:186)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4760)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5184)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:724)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:700)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:714)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:919)
at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1704)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Answer 1

There was a discrepency in the jdk that was installed.
More information: if you are upgrading jdk version, you would have to wipe clean the older versions of jdk and uninstall Jenkins. If you are running Jenkins through Tomcat, that too will have to be uninstalled and everything will have to be re-installed.