Get List of Classes from an object in java

Iam currently trying to create a distinct List<Class> classList which contains all Classes of an object for example

DemoObject.java

public class DemoObject {

    private Integer id;
    private String name;
    private BigDecimal price;
    private Boolean isActive;
    private List<NestedDemoObject> nested;
}

NestedDemoObject.java

public class NestedDemoObject {

    private Integer id;
    private String nameNest;
    private Boolean isActive;
}

What i want to create is a method public List<Class> getDistinctClasses(Class cl); which you give as input for example DemoObject.class and returns a list with

[DemoObject.class, Integer.class, String.class, BigDecimal.class, Boolean.class, List<NestedDemoObject>.class, NestedDemoObject.class]

Another example for NestedDemoObject.class would be

[NestedDemoObject.class, Integer.class, String.class, Boolean.class]

I tried to use the .getDeclaredClasses() from Class without any luck. There is any way to get all nested classes from an object with Reflection API?

Any help or direction appreciated.