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public class AbstractDao<T>{

    private Class<T> clz;

    public AbstractDao(){
        this.clz = (Class<T>)
                ((ParameterizedType)getClass()
                        .getGenericSuperclass())
                        .getActualTypeArguments()[0];
    }
    ...
}

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public class AbstractDao<T>{
    private int tableId;
    
    public AbstractDao(){
        this.tableId = setTableId();
    }
    
    protected abstract int setTableId();
}

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public class UserDao extends AbstractDao<User>{
    
    @Value("${tableid.user}")
    private int userTableId;

    protected int setTableId() {
        return buserTableId;
    }
}

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public class AbstractDao<T>{
    private int tableId;
    
    @PostConstruct
    public init(){
        this.tableId = setTableId();
    }
    
    protected abstract int setTableId();
}

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public class A{
    private long id;
    private String aStr;
}

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public class B{
    private long id;
    private String bStr;
}

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public class C{
    private long id;
    private String aStr;
    private String bStr;
}

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private C getCForAAndB(A a,B b){
    C c = new C();
    c.setId(a.getId());
    c.setAstr(a.getAStr())
    c.setBstr(b.getBStr())
    return c; 
}

private List<C> mergeList(List<A> aList,List<B> bList){
    
    Map<Long,B> bMap = bList.parallelStream()
        .collect(Collectors.toMap(B::getId,b -> b));
        
    return aList.parallelStream()
            .map(a -> getCForAAndB(a,bMap.get(a.getId)))
            .collect(Collectors.toList());
}