Remove Setting Method
Problem
The value of a field should be set only when it's created, and not change at any time after that.
Solution
So remove methods that set the field's value.
Before
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After
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Why Refactor
You want to prevent any changes to the value of a field.
How to Refactor
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The value of a field should be changeable only in the constructor. If the constructor doesn't contain a parameter for setting the value, add one.
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Find all setter calls.
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If a setter call is located right after a call for the constructor of the current class, move its argument to the constructor call and remove the setter.
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Replace setter calls in the constructor with direct access to the field.
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Delete the setter.