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Code Block

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public static final SomeType [] SOMETHINGS = { ... };

This Even though SomeType is immutable, this declaration allows the SOMETHINGS array to be modified by untrusted clients of the code. Any element of the array can be assigned a new value, namely a reference to a new SomeType object.

This noncompliant code example also violates OBJ01-J. Limit accessibility of fields.

Noncompliant Code Example (getter method)

This noncompliant code example complies with OBJ01-J. Limit accessibility of fields by declaring the array private. But, in declaring the array private, this code example violates OBJ05-J. Do not return references to private mutable class members.

Suppose that SomeType is immutable.

Code Block

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private static final SomeType [] SOMETHINGS = { ... };
public static final getSomethings() {return SOMETHINGS;}

Even though SomeType is immutable, the public getter method enables untrusted clients to modify the SOMETHINGS array. Any element of the array can be assigned a new value, namely a reference to a new SomeType object.

Compliant Solution

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(clone)

Continuing with the assumption that SomeType is immutable, one One approach is to have a private array and a public method that returns a copy of the array:

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Now, the original array cannot be modified by any client. If SomeType were mutable, this approach would not be effective because the array clone references the same SomeType objects as the SOMETHINGS array. If the client modified the clone SomeType objects directly, the SomeType objects referenced by the SOMETHINGS array would also change.

Compliant Solution

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(Unmodifiable List)

Continuing with the assumption that SomeType is immutable, an An alternative approach is to have a private array from which a public immutable list is constructed:

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Now, neither the original array values nor the public list can be modified by a client. If SomeType were mutable, this would not be effective because the list references the same SomeType objects as the SOMETHINGS array. The unmodifiabileList prevents the list from being modified, not the elements in the list. If the client modified the list's SomeType objects directly, the SomeType objects referenced by the SOMETHINGS array would also change.