Extract Boolean Variable From Conditional**

Motivation

This situation can be remedied by converting the complex conditional logic into boolean variables and then replacing sections of the conditional expression with those boolean variables.

In this case we are choosing to use local boolean variables rather than converting them to methods using Extract Method (114). A variant on this refactoring, and one which also addresses the "then" and "else" clauses of a complex conditional, is Decompose Conditional(136).

Mechanics

1. Replace sections of, or the entire, complex conditional expression with boolean variables.
2. Place the boolean variables back into the conditional expression.
3. Compile and test.

Example

        if ( (platform.toUpperCase().indexOf("MAC") > -1) &&
             (browser.toUpperCase().indexOf("IE") > -1) &&
              wasInitialized() && resize > 0 )
        {
          // do something
        }

Next, we extract the complex parts of the expression into booleans.

        boolean isMacOs     = platform.toUpperCase().indexOf("MAC") > -1;
  (1)   boolean isIEBrowser = browser.toUpperCase().indexOf("IE")  > -1;
        boolean wasResized  = resize > 0;

Next, we replace the old conditional expression with the new booleans.

  (2)   if (isMacOs && isIEBrowser && wasInitialized() && wasResized)
        {
          // do something
        }

boolean isMacOs     = platform.toUpperCase().indexOf("MAC") > -1;
boolean isIEBrowser = browser.toUpperCase().indexOf("IE")  > -1;
boolean wasResized  = resize > 0;

if (isMacOs && isIEBrowser && wasInitialized() && wasResized)
{
  // do something
}