define in Java

Question

I m beginning to program in Java and I m wondering if the equivalent to the C    define exists     A quick search of google says that it doesn t  but could anyone tell me if something similar exists in Java  I m trying to make my code more readable        Instead of myArray 0  I want to be able to write myArray PROTEINS  for example

User · Answer

Most readable solution is using Static Import  Then you will not need to use AnotherClass constant   Write a class with the constant as public static field    package ConstantPackage   public class Constant       public static int PROTEINS   1      Then just use Static Import where you need the constant   import static ConstantPackage Constant PROTEINS   public class StaticImportDemo        public static void main String  args             int   myArray   new int 5           myArray PROTEINS    0             To know more about Static Import please see this stack overflow question

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Java doesn t have a general purpose define preprocessor directive   In the case of constants  it is recommended to declare them as static finals  like in  private static final int PROTEINS   100    Such declarations would be inlined by the compilers  if the value is a compile-time constant      Please note also that public static final constant fields are part of the public interface and their values shouldn t change  as the compiler inlines them    If you do change the value  you would need to recompile all the sources that referenced that constant field

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Manifold Preprocessor implemented as a javac compiler plugin is designed exclusively for conditional compilation of Java source code  It uses familiar C C   style of directives   define   undef   if   elif   else   endif   error  and  warning  It has Maven and Gradle plugins

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Simplest Answer is  No Direct method of getting it because there is no pre-compiler  But you can do it by yourself  Use classes and then define variables as final so that it can be assumed as constant throughout the program Don t forget to use final and variable as public or protected not private otherwise you won t be able to access it from outside that class

User · Answer

No  because there s no precompiler  However  in your case you could achieve the same thing as follows   class MyClass       private static final int PROTEINS   0                MyArray   foo   new MyArray PROTEINS        The compiler will notice that PROTEINS can never  ever change and so will inline it  which is more or less what you want   Note that the access modifier on the constant is unimportant here  so it could be public or protected instead of private  if you wanted to reuse the same constant across multiple classes

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Java Primitive Specializations Generator supports    with        define    and    if           elif           endif    blocks which allow to do some kind of macro generation in Java code  similar to java-comment-preprocessor mentioned in this answer   JPSG has Maven and Gradle plugins

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Comment space too small  so here is some more information for you on the use of static final  As I said in my comment to the Andrzej s answer  only primitive and String are compiled directly into the code as literals  To demonstrate this  try the following   You can see this in action by creating three classes  in separate files    public class DisplayValue       private String value       public DisplayValue String value            this value   value             public String toString             return value           public class Constants       public static final int INT VALUE   0      public static final DisplayValue VALUE   new DisplayValue  A       public class Test       public static void main String   args            System out println  Int         Constants INT VALUE           System out println  Value       Constants VALUE             Compile these and run Test  which prints   Int      0 Value    A   Now  change Constants to have a different value for each and just compile class Constants  When you execute Test again  without recompiling the class file  it still prints the old value for INT VALUE but not VALUE  For example   public class Constants       public static final int INT VALUE   2      public static final DisplayValue VALUE   new DisplayValue  X        Run Test without recompiling Test java   Int      0 Value    X   Note that any other type used with static final is kept as a reference   Similar to C C    if  endif  a constant literal or one defined through static final with primitives  used in a regular Java if condition and evaluates to false will cause the compiler to strip the byte code for the statements within the if block  they will not be generated    private static final boolean DEBUG   false   if  DEBUG           code here        The code at     code here     would not be compiled into the byte code  But if you changed DEBUG to true then it would be

User · Answer

static final int PROTEINS   1     myArray PROTEINS    You d normally put  constants  in the class itself  And do note that a compiler is allowed to optimize references to it away  so don t change it unless you recompile all the using classes   class Foo     public static final int SIZE   5     public static int   arr   new int SIZE     class Bar     int last   arr Foo SIZE - 1        Edit cycle    SIZE 4  Also compile Bar because you compiler may have just written  4  in the last compilation cycle

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There is preprocessor for Java which provides directives like  define   ifdef   ifndef and many others  for instance PostgresJDBC team uses it to generate sources for different cases and to not duplicate code

[java] #define in Java

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