There are several reasons. First off, it’s not necessary for performance. The JVM already optimizes things at runtime, so there’s no point in adding redundant complexity to the compiler. However, another major reason noone has mentioned here is debugging. Making the bytecode as close to the original source as possible makes it a lot easier … Read more
By default, <javac> runs in-process with Ant. It is a general limitation of Java that you can’t adjust a JVM process’ Xms and Xmx once that JVM process has launched. So, the error message that you are seeing is the software rejecting your attempt to violate this principle (using an unhelpful, unfriendly error message.) If, … Read more
As far as I can see you have the JRE in your PATH, but not the JDK. From a command prompt try this: set PATH=%PATH%;C:\Program Files (x86)\Java\jdk1.7.0_17\bin Then try javac again – if this works you’ll need to permanently modify your environment variables to have PATH include the JDK too.
As mentioned by @Blorgbeard you most likely do not have a Java JDK (Java Development Kit) installed. See this web page for more information about the various versions of Java available for Ubuntu. The following command will install the OpenJDK version of the Java JDK: apt-get install default-jdk
Your file is being read as UTF-8, otherwise a character with value “65279” could never appear. javac expects your source code to be in the platform default encoding, according to the javac documentation: If -encoding is not specified, the platform default converter is used. Decimal 65279 is hex FEFF, which is the Unicode Byte Order … Read more
The BOM is generated by, say, File.WriteAllText() or StreamWriter when you don’t specify an Encoding. The default is to use the UTF8 encoding and generate a BOM. You can tell the java compiler about this with its -encoding command line option. The path of least resistance is to avoid generating the BOM. Do so by … Read more
The addition of parameter names to the class file format is covered by JEP 118, which was delivered in Java 8. There was a little bit of discussion about why inclusion of parameter names was made optional in OpenJDK email threads here and here. Briefly, the stated reasons to make parameter names optional are concerns … Read more
JDK is right. The 2nd method is not more specific than the 1st. From JLS3#15.12.2.5 “The informal intuition is that one method is more specific than another if any invocation handled by the first method could be passed on to the other one without a compile-time type error.” This is clearly not the case here. … Read more
Yes, calling getClass() has become a canonical “test for null” idiom, as getClass() is expected to be a cheap intrinsic operation and, I suppose, HotSpot might be capable of detecting this pattern and reduce the operation to an intrinsic null-check operation, if the result of getClass() is not used. Another example is creating an inner … Read more
Since the field is not only final, but a compile-time constant, it will not get accessed when being read, but the read gets replaced by the constant value itself, the iconst_5 instruction in your case. But the behavior of throwing a NullPointerException when dereferencing null, which would be implied when using a getfield instruction, must … Read more