java.lang.OutOfMemoryError: Java heap space

My application is deployed on a cluster environment. Recently the server went down with the following stacktrace. It doesn't seem to be coming from the code. It was running all right until recently when this error pop up. No major changes were made to the server. Can someone advise?

java.lang.OutOfMemoryError: Java heap space
    at java.lang.AbstractStringBuilder.<init>(AbstractStringBuilder.java:44)
    at java.lang.StringBuilder.<init>(StringBuilder.java:69)
    at java.io.ObjectStreamClass$FieldReflectorKey.<init>(ObjectStreamClass.java:2106)
    at java.io.ObjectStreamClass.getReflector(ObjectStreamClass.java:2039)
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:586)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1552)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1466)
    at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1591)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:348)
    at weblogic.utils.io.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:195)
    at weblogic.rjvm.MsgAbbrevInputStream.readObject(MsgAbbrevInputStream.java:565)
    at weblogic.utils.io.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:191)
    at weblogic.rmi.internal.dgc.DGCServerImpl_WLSkel.invoke(Unknown Source)
    at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:589)
    at weblogic.rmi.internal.BasicServerRef$1.run(BasicServerRef.java:479)
    at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:363)
    at weblogic.security.service.SecurityManager.runAs(Unknown Source)
    at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:475)
    at weblogic.rmi.internal.BasicServerRef.access$300(BasicServerRef.java:59)
    at weblogic.rmi.internal.BasicServerRef$BasicExecuteRequest.run(BasicServerRef.java:1016)
    at weblogic.work.SelfTuningWorkManagerImpl.schedule(SelfTuningWorkManagerImpl.java:126)
    at weblogic.rmi.internal.BasicServerRef.dispatch(BasicServerRef.java:321)
    at weblogic.rmi.internal.BasicServerRef.dispatch(BasicServerRef.java:918)
    at weblogic.rjvm.RJVMImpl.dispatchRequest(RJVMImpl.java:1084)
    at weblogic.rjvm.RJVMImpl.dispatch(RJVMImpl.java:1001)
    at weblogic.rjvm.ConnectionManagerServer.handleRJVM(ConnectionManagerServer.java:240)
    at weblogic.rjvm.ConnectionManager.dispatch(ConnectionManager.java:877)
    at weblogic.rjvm.MsgAbbrevJVMConnection.dispatch(MsgAbbrevJVMConnection.java:446)
    at weblogic.rjvm.t3.MuxableSocketT3.dispatch(MuxableSocketT3.java:368)
    at weblogic.socket.AbstractMuxableSocket.dispatch(AbstractMuxableSocket.java:383)
    at weblogic.socket.SocketMuxer.readReadySocketOnce(SocketMuxer.java:872)

You are running out of memory, which suggests one of the following:

• you need to give your process more memory (with the -Xmx java command line option); or
• you have a memory leak

Without more information, it's hard to say which is the case. The stack trace for an OutOfMemoryError is rarely useful, as it only shows the point at which heap was exhausted; it doesn't show you why your heap is being filled up.