Inserting into a TreeSet in java The Yasser Ibrahim @Jobilize.com

Author: Yasser Ibrahim

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Question 176 / 297: The following code will throw a runtime exception, which line causes the exception?

import java.util.HashSet;
import java.util.Set;
import java.util.TreeSet;

public class Test{
	public static void main(String[] args) {

		Set s = new HashSet();
		s.add("A"); // Line 1
		s.add(new Foo()); // Line 2

		Set t = new TreeSet();
		t.add("A"); // Line 3
		t.add(new Foo()); // Line 4
	}
}

class Foo {}

A Line 1

B Line 2

C Line 3

D Line 4

<< First < Previous Next > Last >>

Explanation:

The two collections are non-generic, so anything is allowed to be added to these two collections.

But since TreeSet is a sorted collection, which means, what inserted in it should be Comparable, line 4 will cause a runtime exception because Foo is not Comparable.

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