通用类型列表的生成器 class

Question

I have a class which have a generic type list, I want to set this field using builder pattern, please help me, I am not able to find any suitable content in the internet

Java Class

public class DialogCar<T> implements Parcelable {

    private String type;
    private List<T> selectedValues;
...

please let me know the Builder class for the above java class

Answer 1

You could parameterize the builder as well:

class DialogCarBuilder<T> {
    private String type;
    private List<T> selectedValues;

    public DialogCarBuilder<T> withType(String type) {
        this.type = type;
        return this;
    }
    
    public DialogCarBuilder<T> withSelectedValues(List<T> selectedValues) {
        this.selectedValues = selectedValues;
        return this;
    }

    public DialogCar<T> build() {
        return new DialogCar<>(type, selectedValues);
    }
}

Then use it:

DialogCarBuilder<Integer> b1 = new DialogCarBuilder<Integer>();
b1.withSelectedValues(... <HERE PASS LIST OF INTEGERS>).build();

Answer 2

Not doing your homework for you, but hints to get you going:

The purpose of a builder pattern is to be able to have multiple calls to collect the data required for the new object before creating it.

So your builder should have a addSelectedValue(T value) " method that simply takes a T value, and adds it to a builder-internal List<T> values list. And then, the your build() method simply passes on that list for example.