java - ClassCastException when casting from Object[] to Comparable[] -


this question has answer here:

edit: noticed post flagged duplicate; read through other, similar, question didn't treat same problem mine. i'm working class guaranteed of type comparable, yet can't cast it.

i have following class, implementation of interface queue. make sure type heappriorityqueue object works implements comparable, method e.compareto(e other) available.

i create instance of heappriorityqueue in main method. patient class implements comparable

heappriorityqueue<patient> queue = new heappriorityqueue<>();

at compilation however, exception classcastexception points towards last line in code below

public class heappriorityqueue<e extends comparable<e>> implements queue<e> {      private final int default_capacity = 10;      private int size;     private e[] array;      public heappriorityqueue()     {         size = 0;         array = (e[]) new object[default_capacity + 1];     } }

the exception:

exception in thread "main" java.lang.classcastexception: [ljava.lang.object; cannot cast [ljava.lang.comparable;

i'm working class guaranteed of type comparable, yet can't cast it.

new object[default_capacity + 1]; doesn't guarantee instead of fact it's object array. object array can't safely cast comparable array.

you'd have use like:

class<e> clazz; array = (e[]) array.newinstance(clazz, size);

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