[Soot-list] Exception: resolving level SIGNATURES / HIERARCHY

[Arvind]

Hi,

I ran soot in whole program mode and got the following exception at this 
line

   SootClass source = Scene.v().getSootClass("java.lang.String");

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Exception in thread "main" java.lang.RuntimeException: This operation 
requires resolving level SIGNATURES but java.lang.String is at resolving 
level HIERARCHY
 	at soot.SootClass.checkLevel(SootClass.java:126)
 	at soot.SootClass.getMethod(SootClass.java:327)
 	at 
pack1.CallGraphPruner._getCompulsoryNodes(CallGraphPruner.java:249)
 	at 
pack1.CallGraphPruner._getCallGraphEntryPoints(CallGraphPruner.java:213)
 	at pack1.CallGraphPruner.<init>(CallGraphPruner.java:108)
 	at pack1.Test.main(Test.java:61)

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Any help would be highly useful.

Regards,
D.Arvind.