Are there inline functions in java

Question

Is there a concept of inline functions in java  or its replaced something else  If there is  how is it used  I ve heard that public  static and final methods are the inline functions  Can we create our own inline function

User · Answer

No  there is no inline function in java  Yes  you can use a public static method anywhere in the code when placed in a public class  The java compiler may do inline expansion on a static or final method  but that is not guaranteed   Typically such code optimizations are done by the compiler in combination with the JVM JIT HotSpot for code segments used very often  Also other optimization concepts like register declaration of parameters are not known in java   Optimizations cannot be forced by declaration in java  but done by compiler and JIT  In many other languages these declarations are often only compiler hints  you can declare more register parameters than the processor has  the rest is ignored    Declaring java methods static  final or private are also hints for the compiler  You should use it  but no garantees  Java performance is dynamic  not static  First call to a system is always slow because of class loading  Next calls are faster  but depending on memory and runtime the most common calls are optimized withinthe running system  so a server may become faster during runtime

User · Answer

Java does not provide a way to manually suggest that a method should be inlined  As  notnoop says in the comments  the inlining is typically done by the JVM at execution time

User · Answer

What you said above is correct  Sometimes final methods are created as inline  but there is no other way to explicitly create an inline function in java

User · Answer

In Java  the optimizations are usually done at the JVM level   At runtime  the JVM perform some  complicated  analysis to determine which methods to inline   It can be aggressive in inlining  and the Hotspot JVM actually can inline non-final methods   The java compilers almost never inline any method call  the JVM does all of that at runtime     They do inline compile time constants  e g  final static primitive values    But not methods   For more resources    Article  The Java HotSpot Performance Engine  Method Inlining Example Wiki  Inlining in OpenJDK  not fully populated but contains links to useful discussions

User · Answer

so  it seems there arent  but you can use this workaround using guava or an equivalent Function class implementation  because that class is extremely simple  ex        assert false   new com google common base Function lt Void String gt              Override public String apply Void input                  your complex code go here             return  weird message              apply null     yes  this is dead code just to exemplify how to create a complex code block  within     to do something so specific that shouldnt bother us on creating any method for it  AKA inline

User · Answer

Real life example   public class Control       public static final long EXPIRED ON   1386082988202l      public static final boolean isExpired             return  System currentTimeMillis    gt  EXPIRED ON             Then in other classes  I can exit if the code has expired   If I reference the EXPIRED ON variable from another class  the constant is inline to the byte code  making it very hard to track down all places in the code that checks the expiry date   However  if the other classes invoke the isExpired   method  the actual method is called  meaning a hacker could replace the isExpired method with another which always returns false   I agree it would be very nice to force a compiler to inline the static final method to all classes which reference it   In that case  you need not even include the Control class  as it would not be needed at runtime   From my research  this cannot be done   Perhaps some Obfuscator tools can do this  or  you could modify your build process to edit sources before compile   As for proving if the method from the control class is placed inline to another class during compile  try running the other class without the Control class in the classpath

User · Answer

Java9 has an  Ahead of time  compiler that does several optimizations at compile-time  rather than runtime  which can be seen as inlining

User · Answer

Well  there are methods could be called  inline  methods in java  but depending on the jvm  After compiling  if the method s machine code is less than 35 byte  it will be transferred to a inline method right away  if the method s machine code is less than 325 byte  it could be transferred into a inline method  depending on the jvm

[java] Are there inline functions in java?

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