Reflecting an array in Java

Question

I am new in Java and have a task to write some application. Faced one problem which can not pass :(

The issue is to update an array element through reflection (app selecting public array to update dinamicaly depending on string app reading from file):

First, i have reflected boolean variables as follows:

activity = activityName(activities[i].substring(0,activities[i].lastIndexOf('.', activities[i].length() - 4)));  
Field field = refClass.getField(activity);  
Object obj = field;  
field.setBoolean(obj, true);

And that worked for me well. But now i need to use arrays instead of regular variables, and tried to make as follows:

activity = activityName(activities[i].substring(0, activities[i].lastIndexOf('.',  activities[i].length() - 4)));  
Field field = refClass.getField(activity);  
Object field_act = field;  
field_act.setBoolean(field_act, LMKStorage.currentLmkSlot, true);

And getting exception "Argument not an array". :(

In field_act.setBoolean(field_act, LMKStorage.currentLmkSlot, true);, field_act is boolean[] i am getting with .getField(activity), LMKStorage.currentLmkSlot is int to determine which position of an array to set and "true" is value to set. The field_act i have to get 100% is an array, because i have not non-array static variables in refClass.

so far i have got studing books i have.But still nothing. Tried to google any examples to update array elements... nothing usefull for me.

Please advice.

why are you using the field_act variable instead of field? Object doesn't have a setBoolean method. Can you post your actual code? — Kane
– Kane, Commented Nov 25, 2011 at 22:19
I'm a little confused by your working example. Your obj variable is the field representation object? obj should be some instance of your refClass. — Neil Essy
– Neil Essy, Commented Nov 25, 2011 at 22:22
Actually, i tried many ways, and field was too. activity = activityName(activities[i].substring(0, activities[i].lastIndexOf('.', activities[i].length() - 4))); Field field = refClass.getField(activity); Object field_act = field; Array.setBoolean(field, LMKStorage.currentLmkSlot, true); Just tried to use field` which is Field type and got: java.lang.IllegalArgumentException: Argument is not an array — Juris
– Juris, Commented Nov 25, 2011 at 22:37
Can't you just retrieve the array with Field.get, cast it to a boolean[], and set the value in that? — millimoose
– millimoose, Commented Nov 25, 2011 at 22:37
Sorry, for mistakes in formating posts, i am first time here and experimenting to get my posts nice. — Juris
– Juris, Commented Nov 25, 2011 at 22:38

True Soft · Accepted Answer · 2011-11-25 22:25:45Z

1

For arrays, use java.lang.reflect.Array instead of java.lang.reflect.Field.

Object field_act = field.get(obj);
Array.setBoolean(field_act, LMKStorage.currentLmkSlot, true);

edited Nov 25, 2011 at 22:25

answered Nov 25, 2011 at 22:15

True Soft

8,7976 gold badges58 silver badges86 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Juris Over a year ago

Yess, You are correct that was my mistake while asking question. The correct code is: Array.setBoolean(field_act, LMKStorage.currentLmkSlot, true);

True Soft Over a year ago

Then the mistake is in your code. You should replace Object field_act = field; with the line Object field_act = field.get(obj);.

Collectives™ on Stack Overflow

Reflecting an array in Java

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related