Why do JVM arguments start with “-D”?

Why couldn’t the architects of Java let us simply do:

java -jar -myProp="Hello World" myProgram.jar

It could work today but suppose that in next Java versions a -myProp argument is introduced as a JVM option.
How to distinguish your -myProp from the -myProp JVM option ? No way.
So it exists an obvious reason to use -D to define system properties.

As other example, instead of -myProp suppose you program relies on a -client system property.
It will not run :

java -jar -client="davidxxx" myProgram.jar

You would have a JVM error such as :

Unrecognized option: -client=davidxxx

as -client is a JVM standard option that expects no value.

But if you use -D-client, it is now fine as here -Dclient is defined as a system property that is distinct from the -client standard JVM option :

java -jar -D-client="davidxxx" myProgram.jar

Or by using both :

java -jar -client -D-client="davidxxx" myProgram.jar

To go further, not all JVM arguments start with -D. but most of them have a prefix (-D, -X, -XX) that allows in a someway to define namespaces.

You have distinct categories of JVM arguments :

1. Standard Options (-D but not only).

These are the most commonly used options that are supported by all implementations of the JVM.

You use -D to specify System properties but most of them don’t have any prefix :-verbose, -showversion, and so for…

2. Non-Standard Options (prefixed with -X)

These options are general purpose options that are specific to the Java HotSpot Virtual Machine.
For example : -Xmssize, -Xmxsize

3. Advanced Runtime Options (prefixed with -XX)

These options control the runtime behavior of the Java HotSpot VM.

4. Advanced JIT Compiler Options (prefixed with -XX)

These options control the dynamic just-in-time (JIT) compilation performed by the Java HotSpot VM.

5. Advanced Serviceability Options (prefixed with -XX)

These options provide the ability to gather system information and perform extensive debugging.

6. Advanced Garbage Collection Options (prefixed with -XX)

These options control how garbage collection (GC) is performed by the Java HotSpot VM.

Related Posts:

  1. Error unable to access jarfile C:\Jar
  2. How do I parse command line arguments in Java?
  3. Running Command Line in Java
  4. What does Java option -Xmx stand for? [duplicate]
  5. How do I convert a String to an int in Java?
  6. What does Java option -Xmx stand for? [duplicate]
  7. Is there an invisible character that is not regarded as whitespace?
  8. Problem with gif with transparent background
  9. Finding white rectangle in an image
  10. 1000 * 60 * 60 * 24 * 30 results in a negative number [duplicate]
  11. How to convert nanoseconds to seconds using the TimeUnit enum?
  12. Search for words with telephone numbers from 2-3-4 tree
  13. Using or ‘|’ in regex [duplicate]
  14. How to format strings in Java
  15. What is the difference between x86 and x64
  16. && (AND) and || (OR) in IF statements
  17. How to use the toString method in Java?
  18. What is a NullPointerException, and how do I fix it?
  19. What exactly is Apache Camel?
  20. Unable to find valid certification path to requested target – error even after cert imported
  21. Unable to find valid certification path to requested target – error even after cert imported
  22. What is the equivalent of the C++ Pair in Java?
  23. Java – Convert integer to string [duplicate]
  24. Getting random numbers in Java [duplicate]
  25. What is an instance variable in Java?
  26. javac is not recognized as an internal or external command, operable program or batch file [closed]
  27. javac is not recognized as an internal or external command, operable program or batch file [closed]
  28. Java: “error: cannot find symbol”
  29. How does the Java ‘for each’ loop work?
  30. What is a StackOverflowError?
  31. How to uninstall Eclipse?
  32. Is GNU’s Java Compiler (GCJ) dead? [closed]
  33. How does System.out.print() work?
  34. How do I “decompile” Java class files? [closed]
  35. How do I determine whether an array contains a particular value in Java?
  36. How to initialize an array in Java?
  37. How does the Java ‘for each’ loop work?
  38. Java 8 Iterable.forEach() vs foreach loop
  39. Initialize part of an array in java
  40. How can I solve Exception in thread “main” java.lang.NullPointerException error [duplicate]
  41. How to split a string in Java
  42. What does “Could not find or load main class” mean?
  43. What does “Could not find or load main class” mean?
  44. Why am I getting a NoClassDefFoundError in Java?
  45. How to avoid “ConcurrentModificationException” while removing elements from `ArrayList` while iterating it? [duplicate]
  46. Eclipse/Maven error: “No compiler is provided in this environment”
  47. How do I compare strings in Java?
  48. What is reflection and why is it useful?
  49. Implementing UML diagram to Java [closed]
  50. How to round a number to n decimal places in Java
  51. Using Pairs or 2-tuples in Java [duplicate]
  52. How do I create a file and write to it?
  53. Could not reserve enough space for object heap
  54. When to use LinkedList over ArrayList in Java?
  55. How to convert a char to a String?
  56. Difference between Arrays.asList(array) and new ArrayList(Arrays.asList(array))
  57. What is the proper way to handle a NumberFormatException when it is expected?
  58. What causes “Unable to access jarfile” error?
  59. What does “Could not find or load main class” mean?
  60. How do you create a dictionary in Java? [closed]
  61. Reading a plain text file in Java
  62. Where is JRE 11? [duplicate]
  63. In laymans terms, what does ‘static’ mean in Java? [duplicate]
  64. How to convert/parse from String to char in java?
  65. Reverse a string in Java
  66. Static Classes In Java
  67. Is there any doubly linked list implementation in Java?
  68. How to set a Timer in Java?
  69. How do I declare and initialize an array in Java?
  70. How to parse JSON in Java
  71. Is there a way to convert all comments into javadoc comments? [Eclipse/Java]
  72. Convert list to array in Java [duplicate]
  73. Reverse a string in Java
  74. Sort an array in Java
  75. Java String Split by “|”
  76. Convert String to double in Java
  77. Exception in thread “main” java.util.NoSuchElementException
  78. Could not reserve enough space for object heap
  79. Converting double to string
  80. What is a JavaBean exactly?
  81. What is the “continue” keyword and how does it work in Java?
  82. “Error occurred during initialization of VM; Could not reserve enough space for object heap” using -Xmx3G
  83. Can’t execute jar- file: “no main manifest attribute”
  84. “Char cannot be dereferenced” error
  85. What’s the simplest way to print a Java array?
  86. javax vs java package
  87. Java String new line
  88. Explanation on Integer.MAX_VALUE and Integer.MIN_VALUE to find min and max value in an array
  89. java.lang.ClassNotFoundException: com.mysql.jdbc.Driver in Eclipse
  90. Initialization of an ArrayList in one line
  91. What does the protected modifier mean?
  92. Can’t execute jar- file: “no main manifest attribute”
  93. “Char cannot be dereferenced” error
  94. What’s the simplest way to print a Java array?
  95. Is there a Heap in java?
  96. Java default constructor
  97. What is a stack trace, and how can I use it to debug my application errors?
  98. How can I convert a char to int in Java? [duplicate]
  99. What’s the difference between map() and flatMap() methods in Java 8?
  100. What is the meaning of “this” in Java?

Leave a Comment