org.intellij.lang.annotations
Annotation Type MagicConstant

@Retention(value=SOURCE)
@Target(value={FIELD,PARAMETER,LOCAL_VARIABLE,ANNOTATION_TYPE,METHOD})
public @interface MagicConstant

This annotation intended to help IDEA to detect and auto-complete int and String constants used as an enumeration. For example, in the Label.Label(String, int) constructor the alignment parameter can be one of the following int constants: Label.LEFT, Label.CENTER or Label.RIGHT

So, if @MagicConstant annotation applied to this constructor, IDEA will check the constructor usages for the allowed values.

E.g.

new Label("text", 0); // 0 is not allowed
 new Label("text", Label.LEFT); // OK
 

@MagicConstant can be applied to:

• Field, local variable, parameter.
  E.g.
  

  @MagicConstant(intValues = {TOP, CENTER, BOTTOM})
   int textPosition;
   

  IDEA will check expressions assigned to the variable for allowed values:

  textPosition = 0; // not allowed
    textPosition = TOP; // OK
   

• Method
  E.g.
  

  @MagicConstant(flagsFromClass = java.lang.reflect.Modifier.class)
    public native int getModifiers();
   

  IDEA will analyse getModifiers() method calls and check if its return value is used with allowed values:
  

  if (aClass.getModifiers() == 3) // not allowed
    if (aClass.getModifiers() == Modifier.PUBLIC) // OK
   

• Annotation class
  Annotation class annotated with @MagicConstant created alias you can use to annotate everything as if it was annotated with @MagicConstant itself.
  E.g.
  

  @MagicConstant(flags = {Font.PLAIN, Font.BOLD, Font.ITALIC}) 

  @interface FontStyle {} 

  IDEA will check constructs annotated with @FontStyle for allowed values:
  @FontStyle int myStyle = 3; // not allowed
  @FontStyle int myStyle = Font.BOLD | Font.ITALIC; // OK
  

The @MagicConstant annotation has SOURCE retention, i.e. it is removed upon compilation and does not create any runtime overhead.

Optional Element Summary

long[]	flags
Class	flagsFromClass
long[]	intValues
String[]	stringValues
Class	valuesFromClass

intValues

public abstract long[] intValues

Returns:

int values (typically named constants) which are allowed here. E.g. void setConfirmOpenNewProject(@MagicConstant(intValues = {OPEN_PROJECT_ASK, OPEN_PROJECT_NEW_WINDOW, OPEN_PROJECT_SAME_WINDOW}) int confirmOpenNewProject);

Default:

{}

stringValues

public abstract String[] stringValues

Returns:

String values (typically named constants) which are allowed here.

Default:

{}

flags

public abstract long[] flags

Returns:

allowed int flags (i.e. values (typically named constants) which can be combined with bitwise or operator (|). Also 0 and -1 are considered allowed. E.g.

Default:

{}

valuesFromClass

public abstract Class valuesFromClass

Returns:

allowed values which are defined in the specified class public static final constants. E.g.

Default:

void.class

flagsFromClass

public abstract Class flagsFromClass

Returns:

allowed int flags which are defined in the specified class public static final constants. E.g. @MagicConstant(flagsFromClass = java.awt.InputEvent.class) int eventMask; eventMask = 10; // not allowed; eventMask = InputEvent.CTRL_MASK | InputEvent.ALT_MASK; // OK

Default:

void.class