test hprof parser lib throw exception calculating length of the primitive values array (HPROF_GC_PRIM_ARRAY_DUMP subrecord).
The simplest way to reproduce the issue is to call JavaValueArray.valueString method (called by JavaObject.toString() for String objects).

java.lang.RuntimeException: invalid array element type: 66
at jdk.test.lib.hprof.model.JavaValueArray.elementSize(JavaValueArray.java:82)
at jdk.test.lib.hprof.model.JavaValueArray.readValueLength(JavaValueArray.java:102)
at jdk.test.lib.hprof.model.JavaLazyReadObject.getValueLength(JavaLazyReadObject.java:68)
at jdk.test.lib.hprof.model.JavaValueArray.getLength(JavaValueArray.java:252)
at jdk.test.lib.hprof.model.JavaValueArray.readValue(JavaValueArray.java:112)
at jdk.test.lib.hprof.model.JavaLazyReadObject.getValue(JavaLazyReadObject.java:79)
at jdk.test.lib.hprof.model.JavaValueArray.valueString(JavaValueArray.java:280)
at jdk.test.lib.hprof.model.JavaValueArray.valueString(JavaValueArray.java:274)
at jdk.test.lib.hprof.model.JavaObject.toString(JavaObject.java:193)

Another issue is JavaObject.toString() method for String objects tries to construct string value of the object from "value" field assuming "value" field is array of char. Actually it's byte array.