反射：查找具有内部字段值的对象

Question

How can we filter out single object from ArrayList where we know inner type class, class member ( Field ) and its value?

pseudo-code:

class MyType {
    public String TITLE;
    public int ID;
}

ArrayList<MyType> myArray; // filled with data

function findRowByColumnValue(ArrayList<T> array, Field column, Object compareValue){
    // list all members of "array"
    // and compare the inner field "column" to "compareValue"
}

// called like this
findRowByColumnValue(myArray, MyType.class.getField("ID"), 2);

Answer 1

Here's a generic method that does what you want, except you pass in the field name , rather than the Field itself, because then you can be sure the Field and Class align. Consider a List with a mixture of instances of different classes, each of type MyClass (but possibly a subclass) - each class may use a different Field for a given column name.

static <T> List<T> findRowByColumnValue(List<T> array, String column, Object compareValue){
    List<T> hits= new ArrayList<T>();
    for (T element : array) {
        if (element != null && compareValue.equals(
          element.getClass().getField(column).get(element)) 
            hits.add(element);
    }
    return hits;
}

You may optimize by caching the Field for a given Class etc, but I wouldn't initially unless you notice a performance problem.