Loop over all fields in a Java class

Question

I have a Java class that has a number of Fields.

I would like to Loop over al lthe fields and do something for the one's that are null.

For example if my class is:

public class ClassWithStuff {     public int inty;     public stringy;              public Stuff;     //many more fields } 

In another location, I'd make a ClassWithStuff object and I would like to go though all the fields in the class. Kind of like this:

for (int i = 0; i < ClassWithStuff.getFields().size(); i++) {       //do stuff with each one } 

Is there any way for me to achieve this?

Answer 1

Use getDeclaredFields on [Class]

ClasWithStuff myStuff = new ClassWithStuff(); Field[] fields = myStuff.getClass().getDeclaredFields(); for(Field f : fields){    Class t = f.getType();    Object v = f.get(myStuff);    if(t == boolean.class && Boolean.FALSE.equals(v))       // found default value    else if(t.isPrimitive() && ((Number) v).doubleValue() == 0)      // found default value    else if(!t.isPrimitive() && v == null)      // found default value } 

(http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Class.html)