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    <p>This is not an answer, but it brings up another point of confusion:</p> <p>I wanted to see if the issue was compile-time evaluation or whether the reflection was actually allowing Java to get around the <code>final</code> keyword. Here's a test program. All I added was another set of getter calls, so there's one before and after each <code>changeField()</code> call.</p> <pre><code>package com.example.gotchas; import java.lang.reflect.Field; public class MostlyFinal { private final int primitiveInt = 42; private final Integer wrappedInt = 42; private final String stringValue = "42"; public int getPrimitiveInt() { return this.primitiveInt; } public int getWrappedInt() { return this.wrappedInt; } public String getStringValue() { return this.stringValue; } public void changeField(String name, Object value) throws IllegalAccessException, NoSuchFieldException { Field field = MostlyFinal.class.getDeclaredField(name); field.setAccessible(true); field.set(this, value); System.out.println("reflection: " + name + " = " + field.get(this)); } public static void main(String[] args) throws IllegalAccessException, NoSuchFieldException { MostlyFinal test = new MostlyFinal(); System.out.println("direct: primitiveInt = " + test.getPrimitiveInt()); test.changeField("primitiveInt", 84); System.out.println("direct: primitiveInt = " + test.getPrimitiveInt()); System.out.println(); System.out.println("direct: wrappedInt = " + test.getWrappedInt()); test.changeField("wrappedInt", 84); System.out.println("direct: wrappedInt = " + test.getWrappedInt()); System.out.println(); System.out.println("direct: stringValue = " + test.getStringValue()); test.changeField("stringValue", "84"); System.out.println("direct: stringValue = " + test.getStringValue()); } } </code></pre> <p>Here's the output I get (under Eclipse, Java 1.6)</p> <pre><code>direct: primitiveInt = 42 reflection: primitiveInt = 84 direct: primitiveInt = 42 direct: wrappedInt = 42 reflection: wrappedInt = 84 direct: wrappedInt = 84 direct: stringValue = 42 reflection: stringValue = 84 direct: stringValue = 42 </code></pre> <p>Why the heck does the direct call to getWrappedInt() change ?</p>
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    1. POModifying final fields in Java
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    1. COThe real question is "why the other two do not change?" And the answer is - because their values are inlined in getters (Tom's answer points to JLS sections describing this behavior). Inlining only happens for primitive types and String (assuming the other conditions like final / constant expression / etc... are satisfied). Thus int and String return 42 from getters; Integer does not. The **actual** values have been changed for all 3 fields. If this is confusing - and it is :-) - decompile the class and you'll see what I mean.
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    2. COah, bizarre........
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