In case of mass class file analyzing (in my case - APICover for JCK) sigtest can fail with IOExcepton because of not closing files:

     [java] Attempt to load class javasoft.sqe.tests.lang.lmbd092.lmbd09201m33.lmbd09201m33$CombinerClazz failed
     [java] java.io.FileNotFoundException: /home/ersh/wrk/jck_build_loc/build/out/coverage/out/jck/JCK-runtime-8/classes/javasoft/sqe/tests/lang/lmbd092/lmbd09201m33/lmbd09201m33.class (Too many open files)
     [java] at java.io.FileInputStream.open(Native Method)
     [java] at java.io.FileInputStream.<init>(FileInputStream.java:131)
     [java] at com.sun.tdk.signaturetest.util.SwissKnife.approveFileInputStream(SwissKnife.java:90)
     [java] at com.sun.tdk.signaturetest.classpath.DirectoryEntry.findClass(DirectoryEntry.java:153)
     [java] at com.sun.tdk.signaturetest.classpath.ClasspathImpl.findClass(ClasspathImpl.java:329)
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:459)
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:384)
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.load(BinaryClassDescrLoader.java:244)
     [java] at com.sun.tdk.signaturetest.core.ClassHierarchyImpl.load(ClassHierarchyImpl.java:217)
     [java] at com.sun.tdk.signaturetest.core.ClassHierarchyImpl.load(ClassHierarchyImpl.java:169)
     [java] at com.sun.tdk.apicover.Main.check(Main.java:409)
     [java] at com.sun.tdk.apicover.Main.run(Main.java:133)
     [java] at com.sun.tdk.apicover.Main.main(Main.java:118)
     [java] Invalid class file: javasoft.sqe.tests.lang.lmbd092.lmbd09201m33.lmbd09201m33$CombinerClazz
     [java] java.lang.ClassNotFoundException: javasoft.sqe.tests.lang.lmbd092.lmbd09201m33.lmbd09201m33$CombinerClazz
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.loadCalls(BinaryClassDescrLoader.java:531)
     [java] at com.sun.tdk.apicover.Main.check(Main.java:411)
     [java] at com.sun.tdk.apicover.Main.run(Main.java:133)
     [java] at com.sun.tdk.apicover.Main.main(Main.java:118)
     [java] Caused by: java.io.FileNotFoundException: /home/ersh/wrk/jck_build_loc/build/out/coverage/out/jck/JCK-runtime-8/classes/javasoft/sqe/tests/lang/lmbd092/lmbd09201m33/lmbd09201m33.class (Too many open files)
     [java] at java.io.FileInputStream.open(Native Method)
     [java] at java.io.FileInputStream.<init>(FileInputStream.java:131)
     [java] at com.sun.tdk.signaturetest.util.SwissKnife.approveFileInputStream(SwissKnife.java:90)
     [java] at com.sun.tdk.signaturetest.classpath.DirectoryEntry.findClass(DirectoryEntry.java:153)
     [java] at com.sun.tdk.signaturetest.classpath.ClasspathImpl.findClass(ClasspathImpl.java:329)
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:459)
     [java] at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.loadCalls(BinaryClassDescrLoader.java:521)
     [java] ... 3 more