Generic polymorphic function

GenericPolymorphicFunctionTest.java

package cz.cez.trading.algo.core;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;

public class GenericPolymorphicFunctionTest {

	@Test
	public void testPolymorphicFunction() {
		assertEquals(4, square(new ContainerOfInt(2)));
	}

	// how to write signature of this function?
	// function is fully polymorhic, ie it doesn't care about the generic type of it's parameter at all
	// raw types are discouraged:
	// private static int square(ContainerOfSomething param) {
	// is this correct and approved by Sonar?:
	private static int square(ContainerOfSomething<?> param) {
		return param.getSomeNumberDerivedFromContent()*param.getSomeNumberDerivedFromContent();
	}
	
	public interface ContainerOfSomething<T> {
		int getSomeNumberDerivedFromContent();
		T getContent();
	}
	
	public class ContainerOfInt implements ContainerOfSomething<Integer> {
		private Integer content;

		public ContainerOfInt(Integer content) {
			this.content = content;
		}

		@Override
		public int getSomeNumberDerivedFromContent() {
			return content;
		}

		@Override
		public Integer getContent() {
			return content;
		}
	}
}

Scratch.java

class Scratch {
public static void main(String[] args) {
List raw = new ArrayList<>();
raw.add(new Animal());
List<?> generic = new ArrayList<>();
generic.add(new Animal());
}

static class Animal {

}

static class Dog extends Animal {

}
}