CODEWITHSUNDEEP
javareflectionstaticprivatefinal
fixitagain
fixitagain

Reputation: 6733

Change private static final field using Java reflection

I have a class with a private static final field that, unfortunately, I need to change it at run-time.

Using reflection I get this error: java.lang.IllegalAccessException: Can not set static final boolean field

Is there any way to change the value?

Field hack = WarpTransform2D.class.getDeclaredField("USE_HACK");
hack.setAccessible(true);
hack.set(null, true);

Upvotes: 583

Views: 395231

Answers (17)

Andrei Marchanka
Andrei Marchanka

Reputation: 39

To make this worked with JDK 21 you can use option -Djdk.reflect.useDirectMethodHandle=false

Make accessable for JDK 11 - 17

public static void setFieldAccessible(Field field) throws Exception {
    field.setAccessible(true);
    Method getDeclaredFields0 = Class.class.getDeclaredMethod("getDeclaredFields0", boolean.class);
    getDeclaredFields0.setAccessible(true);
    Field[] fields = (Field[]) getDeclaredFields0.invoke(Field.class, false);
    for (Field each : fields) {
        if ("modifiers".equals(each.getName())) {
            each.setAccessible(true);
            each.setInt(field, field.getModifiers() & ~Modifier.FINAL);
            break;
        }
    }
}

Upvotes: 2

tesmo
tesmo

Reputation: 215

The top rated answer does not work with the new Reflection implementation of JEP416 in e.g. Java 21 that uses MethodHandles and ignores the flags value on the Field abstraction object.

One solution is to use Unsafe, however with this JEP Unsafe and the important long objectFieldOffset(Field f) and long staticFieldOffset(Field f) methods are getting deprecated for removal so for example this will not work in the future:

final Unsafe unsafe = //..get Unsafe (...and add subsequent --add-opens statements for this to work)
final Field ourField = Example.class.getDeclaredField("changeThis");
final Object staticFieldBase = unsafe.staticFieldBase(ourField);
final long staticFieldOffset = unsafe.staticFieldOffset(ourField);
unsafe.putObject(staticFieldBase, staticFieldOffset, "it works");

I do not recommend this but it is possible in Java 21 with the new reflection implementation when making heavy use of the internal API if really needed.

Java 21+ solution without Unsafe

The gist of it is to use a MethodHandle that can write to a static final field by getting it from the internal getDirectFieldNoSecurityManager(...) method of the Lookup by providing it with a MemberName that is manipulated via Reflection to remove the final flag from it.

You will need to add the following JVM options for this to work:

--add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.lang.reflect=ALL-UNNAMED

public class FinalFieldUtil {

    private static class MemberNameWrapper {

        protected  final Class<?> MEMBER_NAME_CLASS;
        private  final Constructor<?> MEMBER_NAME_CONSTRUCTOR;
        private  final Field MEMBER_NAME_FLAGS_FIELD;
        private  final Method MEMBER_NAME_GET_REFERENCE_KIND_METHOD;

         {
            try {
                MEMBER_NAME_CLASS = Class.forName("java.lang.invoke.MemberName");

                MEMBER_NAME_CONSTRUCTOR = MEMBER_NAME_CLASS.getDeclaredConstructor(Field.class, boolean.class); //e.g. new MemberName(myField, true);
                MEMBER_NAME_CONSTRUCTOR.setAccessible(true);

                MEMBER_NAME_FLAGS_FIELD = MEMBER_NAME_CLASS.getDeclaredField("flags");
                MEMBER_NAME_FLAGS_FIELD.setAccessible(true);

                MEMBER_NAME_GET_REFERENCE_KIND_METHOD = MEMBER_NAME_CLASS.getDeclaredMethod("getReferenceKind");
                MEMBER_NAME_GET_REFERENCE_KIND_METHOD.setAccessible(true);
            } catch (ClassNotFoundException | NoSuchMethodException | NoSuchFieldException e) {
                throw new RuntimeException(e);
            }
        }

        final Object instance;

        public MemberNameWrapper(Field field, boolean makeSetter) {
            try {
                instance = MEMBER_NAME_CONSTRUCTOR.newInstance(field, makeSetter);
                removeFinality(instance);

            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        private final void removeFinality(Object memberNameInstance) throws IllegalAccessException {
            //Manipulate flags to remove hints to it being final
            final int initialFlags = MEMBER_NAME_FLAGS_FIELD.getInt(memberNameInstance);

            if (!Modifier.isFinal(initialFlags)) {
                return;
            }

            final int nonFinalFlags = initialFlags & ~Modifier.FINAL;

            MEMBER_NAME_FLAGS_FIELD.setInt(memberNameInstance, nonFinalFlags);
        }

        protected Object getMemberNameInstance(){
            return instance;
        }

        protected byte getReferenceKind() {
            try {
                return (byte) MEMBER_NAME_GET_REFERENCE_KIND_METHOD.invoke(instance);
            } catch (IllegalAccessException | InvocationTargetException e) {
                throw new RuntimeException(e);
            }
        }

    }

    private static class LookupWrapper {

        private  final Class<?> LOOKUP_CLASS;
        private  final Method LOOKUP_GET_FIELD_VAR_HANDLE_NO_SECURITY_MANAGER_METHOD;

         {
            try {
                LOOKUP_CLASS = Lookup.class;
                LOOKUP_GET_FIELD_VAR_HANDLE_NO_SECURITY_MANAGER_METHOD = LOOKUP_CLASS.getDeclaredMethod("getDirectFieldNoSecurityManager", byte.class, Class.class, Class.forName("java.lang.invoke.MemberName"));
                LOOKUP_GET_FIELD_VAR_HANDLE_NO_SECURITY_MANAGER_METHOD.setAccessible(true);

            } catch (NoSuchMethodException | ClassNotFoundException e) {
                throw new RuntimeException(e);
            }

         }

        private final Lookup lookup;

        private LookupWrapper(Lookup lookup) {
            this.lookup = lookup;
        }

        public MethodHandle unreflectVarHandleUnrestricted(Field field) {
            final MemberNameWrapper memberNameSetterWrapper = new MemberNameWrapper(field, true);
            final byte setterReferenceKind = memberNameSetterWrapper.getReferenceKind();
            final Object memberNameSetter = memberNameSetterWrapper.getMemberNameInstance();


            try {
                return (MethodHandle) LOOKUP_GET_FIELD_VAR_HANDLE_NO_SECURITY_MANAGER_METHOD.invoke(lookup, setterReferenceKind, field.getDeclaringClass(), memberNameSetter);
            } catch (IllegalAccessException | InvocationTargetException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public static void setStaticFinalField(Field field, Object value) throws Throwable {
        if (Modifier.isFinal(field.getModifiers()) && field.getType().isPrimitive()) {
            throw new IllegalArgumentException("primitive finals are not supported, because their modification depends on very specific circumstances.");
        }

        final LookupWrapper lookupWrapper = new LookupWrapper(MethodHandles.privateLookupIn(field.getDeclaringClass(), MethodHandles.lookup()));
        final MethodHandle methodHandle = lookupWrapper.unreflectVarHandleUnrestricted(field);
        methodHandle.invoke(value);

    }

}

And then you can

public class TestModelClassWithFinalFields {

    public static final String myStr; //can be set
    public static final List<Object> myList = List.of(); //can be set
    public static final String myInlineStr = "init"; //cannot be set with this method!
    
    static {
        myStr = "initial static value";
    }
}

FinalFieldUtil.setStaticFinalField(TestModelClassWithFinalFields.class.getDeclaredField("myStr"), "new value!");

System.out.println(FinalFieldUtil.myStr);

Please note that this will not work for pure String literals and primitive values when set inline (e.g. static final String = "str")

See my answer here for a the initial attempt and thoughts regarding using the internal API to set a final field in Java 21 without Unsafe.

Upvotes: 1

user24348089
user24348089

Reputation: 1

In openjdk17 I had to remove final modifier not just from Field.modifiers, but also from Field.root.modifiers.
Field.root is used internally in field.set(...) here.
So my code is this:

    private static void makeStaticFinalFieldWritable( Field field ) {
      try {
        var lookup = MethodHandles.privateLookupIn( field.getClass(), MethodHandles.lookup() );
        var modifiersHandle = lookup.findVarHandle( field.getClass(), "modifiers", int.class );
        var modifiers = field.getModifiers();
        modifiersHandle.set( field, modifiers & ~Modifier.FINAL );

        var rootHandle = lookup.findVarHandle( field.getClass(), "root", Field.class );
        var root = ( Field ) rootHandle.get( field );
        if ( root != null && root != field ) {
          makeStaticFinalFieldWritable( root );
        }
      }
      catch ( IllegalAccessException | NoSuchFieldException e ) {
        throw new Error( e );
      }
    }

Upvotes: -1

bric3
bric3

Reputation: 42293

With JDK 18 this won't be possible anymore due to the reimplementation of the core reflection over invokedynamic and MethodHandles as part of JEP-416 (PR).

Quote of Mandy Chung – who is the main author of this incredible work – in the following comment. Emphasis are mine.

If the underlying field is final, a Field object has write access if and only if

  • setAccessible(true) has succeeded for this Field object;
  • the field is non-static; and
  • the field's declaring class is not a hidden class; and
  • the field's declaring class is not a record class.

Upvotes: 6

pringi
pringi

Reputation: 4682

Since Java 12 onwards, the answers given will not work.

Here is an example on how to modify a private static final field since Java 12 (based on this answer).

  private Object modifyField(Object newFieldValue, String fieldName, Object classInstance) throws NoSuchFieldException, IllegalAccessException {
    Field field = classInstance.getClass().getDeclaredField(fieldName);
    VarHandle MODIFIERS;

    field.setAccessible(true);

    var lookup = MethodHandles.privateLookupIn(Field.class, MethodHandles.lookup());
    MODIFIERS = lookup.findVarHandle(Field.class, "modifiers", int.class);
    int mods = field.getModifiers();

    if (Modifier.isFinal(mods)) {
      MODIFIERS.set(field, mods & ~Modifier.FINAL);
    }

    Object previousValue = field.get(classInstance);
    field.set(null, newFieldValue);

    return previousValue;
  }

See this thread for more details.

Upvotes: 6

Some Name
Some Name

Reputation: 9540

Even in spite of being final a field can be modified outside of static initializer and (at least JVM HotSpot) will execute the bytecode perfectly fine.

The problem is that Java compiler does not allow this, but this can be easily bypassed using objectweb.asm. Here is p̶e̶r̶f̶e̶c̶t̶l̶y̶ ̶v̶a̶l̶i̶d̶ ̶c̶l̶a̶s̶s̶f̶i̶l̶e̶ an invalid classfile from the JVMS specification standpoint, but it passes bytecode verification and then is successfully loaded and initialized under JVM HotSpot OpenJDK12:

ClassWriter cw = new ClassWriter(0);
cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, "Cl", null, "java/lang/Object", null);
{
    FieldVisitor fv = cw.visitField(Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL, "fld", "I", null, null);
    fv.visitEnd();
}
{
    // public void setFinalField1() { //... }
    MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC, "setFinalField1", "()V", null, null);
    mv.visitMaxs(2, 1);
    mv.visitInsn(Opcodes.ICONST_5);
    mv.visitFieldInsn(Opcodes.PUTSTATIC, "Cl", "fld", "I");
    mv.visitInsn(Opcodes.RETURN);
    mv.visitEnd();
}
{
    // public void setFinalField2() { //... }
    MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC, "setFinalField2", "()V", null, null);
    mv.visitMaxs(2, 1);
    mv.visitInsn(Opcodes.ICONST_2);
    mv.visitFieldInsn(Opcodes.PUTSTATIC, "Cl", "fld", "I");
    mv.visitInsn(Opcodes.RETURN);
    mv.visitEnd();
}
cw.visitEnd();

In Java, the class looks roughly speaking as follows:

public class Cl{
    private static final int fld;

    public static void setFinalField1(){
        fld = 5;
    }

    public static void setFinalField2(){
        fld = 2;
    }
}

which cannot be compiled with javac, but can be loaded and executed by JVM.

JVM HotSpot has special treatment of such classes in the sense that it prevents such "constants" from participating in constant folding. This check is done on the bytecode rewriting phase of class initialization:

// Check if any final field of the class given as parameter is modified
// outside of initializer methods of the class. Fields that are modified
// are marked with a flag. For marked fields, the compilers do not perform
// constant folding (as the field can be changed after initialization).
//
// The check is performed after verification and only if verification has
// succeeded. Therefore, the class is guaranteed to be well-formed.
InstanceKlass* klass = method->method_holder();
u2 bc_index = Bytes::get_Java_u2(bcp + prefix_length + 1);
constantPoolHandle cp(method->constants());
Symbol* ref_class_name = cp->klass_name_at(cp->klass_ref_index_at(bc_index));
if (klass->name() == ref_class_name) {
   Symbol* field_name = cp->name_ref_at(bc_index);
   Symbol* field_sig = cp->signature_ref_at(bc_index);

   fieldDescriptor fd;
   if (klass->find_field(field_name, field_sig, &fd) != NULL) {
      if (fd.access_flags().is_final()) {
         if (fd.access_flags().is_static()) {
            if (!method->is_static_initializer()) {
               fd.set_has_initialized_final_update(true);
            }
          } else {
            if (!method->is_object_initializer()) {
              fd.set_has_initialized_final_update(true);
            }
          }
        }
      }
    }
}

The only restriction that JVM HotSpot checks is that the final field should not be modified outside of the class that the final field is declared at.

Upvotes: 7

d4vidi
d4vidi

Reputation: 2537

Many of the answers here are useful, but I've found none of them to work on Android, in particular. I'm even a pretty hefty user of Reflect by joor, and neither it nor apache's FieldUtils - both mentioned here in some of the answers, do the trick.

Problem with Android

The fundamental reason why this is so is because on Android there's no modifiers field in the Field class, which renders any suggestion involving this code (as in the marked answer), useless:

Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

In fact, to quote from FieldUtils.removeFinalModifier():

// Do all JREs implement Field with a private ivar called "modifiers"?
final Field modifiersField = Field.class.getDeclaredField("modifiers");

So, the answer is no...

Solution

Pretty easy - instead of modifiers, the field name is accessFlags. This does the trick:

Field accessFlagsField = Field.class.getDeclaredField("accessFlags");
accessFlagsField.setAccessible(true);
accessFlagsField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

Side-note #1: this can work regardless of whether the field is static in the class, or not.

Side-note #2: Seeing that the field itself could be private, it's recommended to also enable access over the field itself, using field.setAccessible(true) (in addition to accessFlagsField.setAccessible(true).

Upvotes: 3

Philip Rego
Philip Rego

Reputation: 648

If your field is simply private you can do this:

MyClass myClass= new MyClass();
Field aField= myClass.getClass().getDeclaredField("someField");
aField.setAccessible(true);
aField.set(myClass, "newValueForAString");

and throw/handle NoSuchFieldException

Upvotes: 0

iirekm
iirekm

Reputation: 9446

I also integrated it with joor library

Just use 

      Reflect.on(yourObject).set("finalFieldName", finalFieldValue);

Also I fixed an issue with override which the previous solutions seem to miss. However use this very carefully, only when there's no other good solution.

Upvotes: 10

polygenelubricants
polygenelubricants

Reputation: 384006

Assuming no SecurityManager is preventing you from doing this, you can use setAccessible to get around private and resetting the modifier to get rid of final, and actually modify a private static final field.

Here's an example:

import java.lang.reflect.*;

public class EverythingIsTrue {
   static void setFinalStatic(Field field, Object newValue) throws Exception {
      field.setAccessible(true);

      Field modifiersField = Field.class.getDeclaredField("modifiers");
      modifiersField.setAccessible(true);
      modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

      field.set(null, newValue);
   }
   public static void main(String args[]) throws Exception {      
      setFinalStatic(Boolean.class.getField("FALSE"), true);

      System.out.format("Everything is %s", false); // "Everything is true"
   }
}

Assuming no SecurityException is thrown, the above code prints "Everything is true".

What's actually done here is as follows:

  • The primitive boolean values true and false in main are autoboxed to reference type Boolean "constants" Boolean.TRUE and Boolean.FALSE
  • Reflection is used to change the public static final Boolean.FALSE to refer to the Boolean referred to by Boolean.TRUE
  • As a result, subsequently whenever a false is autoboxed to Boolean.FALSE, it refers to the same Boolean as the one refered to by Boolean.TRUE
  • Everything that was "false" now is "true"

Related questions

Caveats

Extreme care should be taken whenever you do something like this. It may not work because a SecurityManager may be present, but even if it doesn't, depending on usage pattern, it may or may not work.

JLS 17.5.3 Subsequent Modification of Final Fields

In some cases, such as deserialization, the system will need to change the final fields of an object after construction. final fields can be changed via reflection and other implementation dependent means. The only pattern in which this has reasonable semantics is one in which an object is constructed and then the final fields of the object are updated. The object should not be made visible to other threads, nor should the final fields be read, until all updates to the final fields of the object are complete. Freezes of a final field occur both at the end of the constructor in which the final field is set, and immediately after each modification of a final field via reflection or other special mechanism.

Even then, there are a number of complications. If a final field is initialized to a compile-time constant in the field declaration, changes to the final field may not be observed, since uses of that final field are replaced at compile time with the compile-time constant.

Another problem is that the specification allows aggressive optimization of final fields. Within a thread, it is permissible to reorder reads of a final field with those modifications of a final field that do not take place in the constructor.

See also

  • JLS 15.28 Constant Expression
    • It's unlikely that this technique works with a primitive private static final boolean, because it's inlineable as a compile-time constant and thus the "new" value may not be observable

Appendix: On the bitwise manipulation

Essentially,

field.getModifiers() & ~Modifier.FINAL

turns off the bit corresponding to Modifier.FINAL from field.getModifiers(). & is the bitwise-and, and ~ is the bitwise-complement.

See also

Remember Constant Expressions

Still not being able to solve this?, have fallen onto depression like I did for it? Does your code looks like this?

public class A {
    private final String myVar = "Some Value";
}

Reading the comments on this answer, specially the one by @Pshemo, it reminded me that Constant Expressions are handled different so it will be impossible to modify it. Hence you will need to change your code to look like this:

public class A {
    private final String myVar;

    private A() {
        myVar = "Some Value";
    }
}

if you are not the owner of the class... I feel you!

For more details about why this behavior read this?

Upvotes: 1033

erickson
erickson

Reputation: 269877

If the value assigned to a static final boolean field is known at compile-time, it is a constant. Fields of primitive or String type can be compile-time constants. A constant will be inlined in any code that references the field. Since the field is not actually read at runtime, changing it then will have no effect.

The Java language specification says this:

If a field is a constant variable (§4.12.4), then deleting the keyword final or changing its value will not break compatibility with pre-existing binaries by causing them not to run, but they will not see any new value for the usage of the field unless they are recompiled. This is true even if the usage itself is not a compile-time constant expression (§15.28)

Here's an example:

class Flag {
  static final boolean FLAG = true;
}

class Checker {
  public static void main(String... argv) {
    System.out.println(Flag.FLAG);
  }
}

If you decompile Checker, you'll see that instead of referencing Flag.FLAG, the code simply pushes a value of 1 (true) onto the stack (instruction #3).

0:   getstatic       #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3:   iconst_1
4:   invokevirtual   #3; //Method java/io/PrintStream.println:(Z)V
7:   return

Upvotes: 69

nndru
nndru

Reputation: 2107

Along with top ranked answer you may use a bit simpliest approach. Apache commons FieldUtils class already has particular method that can do the stuff. Please, take a look at FieldUtils.removeFinalModifier method. You should specify target field instance and accessibility forcing flag (if you play with non-public fields). More info you can find here.

Upvotes: 8

Tom&#225;š Z&#225;lusk&#253;
Tom&#225;š Z&#225;lusk&#253;

Reputation: 12090

The accepted answer worked for me until deployed on JDK 1.8u91. Then I realized it failed at field.set(null, newValue); line when I had read the value via reflection before calling of setFinalStatic method.

Probably the read caused somehow different setup of Java reflection internals (namely sun.reflect.UnsafeQualifiedStaticObjectFieldAccessorImpl in failing case instead of sun.reflect.UnsafeStaticObjectFieldAccessorImpl in success case) but I didn't elaborate it further.

Since I needed to temporarily set new value based on old value and later set old value back, I changed signature little bit to provide computation function externally and also return old value:

public static <T> T assignFinalField(Object object, Class<?> clazz, String fieldName, UnaryOperator<T> newValueFunction) {
    Field f = null, ff = null;
    try {
        f = clazz.getDeclaredField(fieldName);
        final int oldM = f.getModifiers();
        final int newM = oldM & ~Modifier.FINAL;
        ff = Field.class.getDeclaredField("modifiers");
        ff.setAccessible(true);
        ff.setInt(f,newM);
        f.setAccessible(true);

        T result = (T)f.get(object);
        T newValue = newValueFunction.apply(result);

        f.set(object,newValue);
        ff.setInt(f,oldM);

        return result;
    } ...

However for general case this would not be sufficient.

Upvotes: 2

VanagaS
VanagaS

Reputation: 3698

In case of presence of a Security Manager, one can make use of AccessController.doPrivileged

Taking the same example from accepted answer above:

import java.lang.reflect.*;

public class EverythingIsTrue {
    static void setFinalStatic(Field field, Object newValue) throws Exception {
        field.setAccessible(true);
        Field modifiersField = Field.class.getDeclaredField("modifiers");

        // wrapping setAccessible 
        AccessController.doPrivileged(new PrivilegedAction() {
            @Override
            public Object run() {
                modifiersField.setAccessible(true);
                return null;
            }
        });

        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        field.set(null, newValue);
    }

    public static void main(String args[]) throws Exception {      
      setFinalStatic(Boolean.class.getField("FALSE"), true);
      System.out.format("Everything is %s", false); // "Everything is true"
    }
}

In lambda expression, AccessController.doPrivileged, can be simplified to:

AccessController.doPrivileged((PrivilegedAction) () -> {
    modifiersField.setAccessible(true);
    return null;
});

Upvotes: 7

hasskell
hasskell

Reputation: 441

Just saw that question on one of the interview question, if possible to change final variable with reflection or in runtime. Got really interested, so that what I became with:

 /**
 * @author Dmitrijs Lobanovskis
 * @since 03/03/2016.
 */
public class SomeClass {

    private final String str;

    SomeClass(){
        this.str = "This is the string that never changes!";
    }

    public String getStr() {
        return str;
    }

    @Override
    public String toString() {
        return "Class name: " + getClass() + " Value: " + getStr();
    }
}

Some simple class with final String variable. So in the main class import java.lang.reflect.Field;

/**
 * @author Dmitrijs Lobanovskis
 * @since 03/03/2016.
 */
public class Main {


    public static void main(String[] args) throws Exception{

        SomeClass someClass = new SomeClass();
        System.out.println(someClass);

        Field field = someClass.getClass().getDeclaredField("str");
        field.setAccessible(true);

        field.set(someClass, "There you are");

        System.out.println(someClass);
    }
}

The output will be as follows:

Class name: class SomeClass Value: This is the string that never changes!
Class name: class SomeClass Value: There you are

Process finished with exit code 0

According to documentation https://docs.oracle.com/javase/tutorial/reflect/member/fieldValues.html

Upvotes: 2

Stephan Markwalder
Stephan Markwalder

Reputation: 201

A little curiosity from the Java Language Specification, chapter 17, section 17.5.4 "Write-protected Fields":

Normally, a field that is final and static may not be modified. However, System.in, System.out, and System.err are static final fields that, for legacy reasons, must be allowed to be changed by the methods System.setIn, System.setOut, and System.setErr. We refer to these fields as being write-protected to distinguish them from ordinary final fields.

Source: http://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.5.4

Upvotes: 20

thecoop
thecoop

Reputation: 46158

The whole point of a final field is that it cannot be reassigned once set. The JVM uses this guarentee to maintain consistency in various places (eg inner classes referencing outer variables). So no. Being able to do so would break the JVM!

The solution is not to declare it final in the first place.

Upvotes: -5

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