Question

Can we create an immutable object without having all fields final?

If possible a couple of examples would be helpful.

Answer 1

Declare all fields private and only define getters:

public final class Private{
    private int a;
    private int b;

    public int getA(){return this.a;}
    public int getB(){return this.b;}
}

citing @Jon Skeet’s comment, final class modifier is useful for:

While an instance of just Private is immutable, an instance of a
subclass may well be mutable. So code receiving a reference of type
Private can’t rely on it being immutable without checking that it’s an
instance of just Private.

So if you want to be sure the instance you are referring to is immutable you should use also final class modifier.