基于propertyName和keyExtractor

Question

我正在尝试编写使用Comparator的通用Function来获取基于propertyName的值进行比较，并希望避免在几个地方进行投射。 以下是我希望避免使用强制转换的代码和地点：

public class Catalog {
    private Integer id = null;
    private String name = null;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Catalog withId(Integer id){
        setId(id);
        return this;
    }


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Catalog withName(String name){
        setName(name);
        return this;
    }
}

    private < U extends Comparable<? super U> > Optional< Comparator<Catalog> > createComparator(String property, boolean ignoreCase){
        Optional< Function<Catalog, U > > keyExtractor = getKeyExtractor(property, ignoreCase);
        if ( !keyExtractor.isPresent() ) return Optional.empty();        
        return Optional.of( Comparator.comparing( keyExtractor.get() ) );
    }

    private < U extends Comparable<? super U> > Optional< Function< Catalog, U > > getKeyExtractor(String property, boolean ignoreCase){
        Optional< Function<Catalog, U > > keyExtractor = getKeyExtractor(property);
        if ( !keyExtractor.isPresent() ) return Optional.empty(); 

        return Optional.of( c -> {
            if (c == null) return null;
            U value = keyExtractor.get().apply(c);
            if (value instanceof String) return ignoreCase ? (U)( (String)value ).toLowerCase() : value;  //NEED TO AVOID CASTING      
            return value;
        } );
    }

    private < U extends Comparable<? super U> > Optional< Function< Catalog, U > > getKeyExtractor(String property){
        if ( "id".equalsIgnoreCase(property) ) return Optional.of( (c) -> (U)c.getId() ); //NEED TO AVOID CASTING
        else if ( "name".equalsIgnoreCase(property) ) return Optional.of( (c) -> (U)c.getName() ); //NEED TO AVOID CASTING
        else return Optional.empty();
    }