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class Foo {
  private final Helper helper;

  public Helper getHelper() {
    return helper;
  }

  public Foo() {
    // Point 1
    helper = new Helper(42);
    // Point 2
  }
}

Wiki MarkupHowever, this solution requires the assignment of a new {{Helper}} instance to {{helper}} from Foo's constructor. According to the _Java Language Specification_, [§17, §17.5.2, "Reading Final Fields During Construction"|http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.5.2] \[[JLS 2005|AA. References#JLS 05]\]Construction" [JLS 2005]

A read of a final field of an object within the thread that constructs that object is ordered with respect to the initialization of that field within the constructor by the usual happens-before rules. If the read occurs after the field is set in the constructor, it sees the value the final field is assigned; otherwise, it sees the default value.

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The helper field should be declared final to document the class's immutability.unmigrated-wiki-markup

According to JSR-133, Section 9.2.3, "Static Final Fields" \[ [JSR-133 2004|AA. References#JSR-133 04]\]

The rules for class initialization ensure that any thread that reads a static field will be synchronized with the static initialization of that class, which is the only place where static final fields can be set. Thus, no special rules in the JMM are needed for static final fields.

Compliant Solution (Immutable Object - Final Fields, Volatile Reference)

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The JMM guarantees that any final fields of an object are fully initialized before a published object becomes visible \[ [Goetz 2006a|AA. References#Goetz 06]\]. By declaring {{n}} declaring n final, the {{Helper}} class is made [immutable|BB. Glossary#immutable]. Furthermore, if the {{helper}} field is declared volatile in compliance with rule [VNA01-J. Ensure visibility of shared references to immutable objects], {{Helper}}'s reference is guaranteed to be made visible to any thread that calls {{getHelper()}} only after {{Helper}} has been fully initialized.

Code Block
bgColor #CCCCFF
class Foo { private volatile Helper helper; public Helper getHelper() { return helper; } public void initialize() { helper = new Helper(42); } } // Immutable Helper public final class Helper { private final int n; public Helper(int n) { this.n = n; } // ... }

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Rule	Severity	Likelihood	Remediation Cost	Priority	Level
TSM03-J	medium	probable	medium	P8	L2

Bibliography

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      11. Thread-Safety Miscellaneous (TSM)      12. Input Output (FIO)