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I have a int variable which hold multiple flags, for instance:
int styles = ExpandableComposite.TITLE_BAR | ExpandableComposite.TWISTIE | ExpandableComposite.EXPANDED;
I can test the presence of a flag
boolean expanded = (styles & ExpandableComposite.EXPANDED) != 0;
How can I clear the value of a flag from styles, i.e. dynamically remove ExpandableComposite.EXPANDED, without knowing the exact flags which are set in styles?
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Enum Flags Attribute The idea of Enum Flags is to take an enumeration variable and allow it hold multiple values. It should be used whenever the enum represents a collection of flags, rather than representing a single value. Such enumeration collections are usually manipulated using bitwise operators.
Flag is used as a signal in a program. Its use is not limited to just C programming, it can be used in just about any code, language independent. Its purpose is to control the program's execution and is also used to debug the program in some cases.
A "flag" variable is simply a boolean variable whose contents is "true" or "false". You can use either the bool type with true or false , or an integer variable with zero for "false" and non-zero for "true".
this is an old C idiom, still working in Java:
styles &= ~ExpandableComposite.EXPANDED;
However these days (>= Java 1.5) you should consider using:
Enum (see Tutorial)EnumSet EnumMap
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