For JDK6 you can download the source from [java.net][1]. For `java.lang` the story begins at `j2se/src/share/native/java/lang/`, and then search... JDK7 rearranges the directory structure a little.

Some methods, such as `Object.hashCode`, may be implemented by hotspot instead or in addition to through JNI/Java.

JDK6 is freely licensed through the Java Research License (JRL) and Java Internal Use License (JIUL). JDK7 and OpenJDK6 is licensed under GPL 2 with CLASSPATH exception (roughly speaking you can link to it without catching the GNU virus). I am not a lawyer.

(&lt;strike&gt;BTW: The real lawyers would like to point out that I am still an employee of Sun Microsystems.&lt;/strike&gt; Sun UK is no more. It is *now* Oracle.)

Update (Adding location for Thread.c):
http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/9b8c96f96a0f/src/share/native/java/lang/Thread.c

  [1]: https://openjdk.java.net/projects/jdk6/

You can look at the source code for [OpenJDK](http://openjdk.java.net/) (licensed under [GPLv2 with Classpath Exception](http://openjdk.java.net/legal/gplv2+ce.html)). Probably the best way to study the JDK implementation internals, unless you want to be bound by the [Java Research Licence](http://www.java.net/jrl.csp), in which case you can access the actual [JDK 6 source](https://jdk6.dev.java.net/).

Do you know if there is a list with all the reference implementation for every component of Java EE 6? I.e. GlassFish is the reference container, Hibernate Validator for validation, etc.


Where can I find a list of all the reference implementations for Java EE 6?

I have to manage a log where i have to see the number of rows that are inserted by a transaction. Is there any way of doing it dynamically ?

How to get number of rows inserted by a transaction

I&#39;m vaguely familiar with the &lt;a href=&quot;http://en.wikipedia.org/wiki/Java_Native_Interface&quot;&gt;JNI&lt;/a&gt;, and I&#39;m curious to see my machine-specific implementation for some native methods in the java.lang package. `Thread#currentThread()`, for example.

I&#39;ve found a bunch of DLLs in [JDK_HOME]/jre/bin, but like I said I&#39;m trying to find the source code.

Does anyone know where the native source code can be found? Is it even available, or is it classified by Sun (oops I mean &quot;We&#39;re In It To Win It&quot; Oracle)?

Where to find source code for java.lang native methods?

I'm vaguely familiar with the <a href="<a href=" http:="" en.wikipedia.org="" wiki="" java_native_interface&#x26;quot;&#x26;gt;jni&#x26;lt;="" a&#x26;gt&#x22;="">http://en.wikipedia.org/wiki/Java_Native_Interface">JNI&#x3C;/a></a>;, and I'm curious to see my machine-specific implementation for some native methods in the java.lang package. <code>Thread#currentThread()</code>, for example.
I've found a bunch of DLLs in [JDK_HOME]/jre/bin, but like I said I'm trying to find the source code.
Does anyone know where the native source code can be found? Is it even available, or is it classified by Sun (oops I mean "We're In It To Win It" Oracle)?

HI,
I like to know can I increase the memory of the JVM depending on my application.If yes how can I increase the JVM memory?
And how can I know the size of JVM?

How can I increase the JVM memory?

I am writing a little code in J2ME. I have a class with a method `setTableId(Short tableId)`. Now when I try to write `setTableId(100)` it gives compile time error. How can I set the short value without declaring another short variable?

When setting `Long` value I can use `setLongValue(100L)` and it works. So, what does `L` mean here and what&#39;s the character for `Short` value? 

Thanks

Setting Short Value Java

I am using log4j with tomcat. When I log exceptions in my JSPs, servlets:

    private Logger _log = Logger.getLogger(this.getClass());
    ...
    try{...} catch (Exception e) {
        _log.error(&quot;Error refreshing all prices&quot;, e);
    }

I only get the first line of the exception, without a stacktrace. 

&gt; 17-Feb 17:37:45 ERROR AutoContrib:175 - Exception while publishing csv file:
java.lang.ArrayIndexOutOfBoundsException


Not very helpful at all!

My log4j.properties file (/tomcat/common/classes/log4j.properties) looks like this:

    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.Target=System.out
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=%d{dd-MMM HH:mm:ss} %5p %c{1}:%L - %m%n
    log4j.appender.stdout.threshold=info

    log4j.appender.file=org.apache.log4j.RollingFileAppender
    log4j.appender.file.maxFileSize=5000KB
    log4j.appender.file.maxBackupIndex=10
    log4j.appender.file.File=${catalina.home}/logs/web.log
    log4j.appender.file.layout=org.apache.log4j.PatternLayout
    log4j.appender.file.layout.ConversionPattern=%d{dd-MMM HH:mm:ss} %5p %c{1}:%L - %m%n
    log4j.appender.file.threshold=info

    log4j.rootLogger=debug, stdout, file

log4j not printing the stacktrace for exceptions

How could I check if string has already been encoded? 

For example, if I encode `TEST==`, I get `TEST%3D%3D`. If I again encode last string, I get `TEST%253D%253D`, I would have to know before doing that if it is already encoded...

I have encoded parameters saved, and I need to search for them. I don&#39;t know for input parameters, what will they be - encoded or not, so I have to know if I have to encode or decode them before search.

How to find out if string has already been URL encoded?

The library in question is [Tokyo Cabinet][1].

I want is to have the native library, JNI library, and all Java API classes in one JAR file to avoid redistribution headaches.

There seems to be [an attempt at this at GitHub][2], but

 1. It does not include the actual native library, only JNI library.
 2. It seems to be specific to [Leiningen][3]&#39;s native dependencies plugin (it won&#39;t work as a redistributable).

The question is, can I bundle everything in one JAR and redistribute it? If yes, how?

P.S.: Yes, I realize it may have portability implications.


  [1]: http://1978th.net/tokyocabinet/
  [2]: http://github.com/lancepantz/tokyocabinet
  [3]: http://github.com/technomancy/leiningen

How to bundle a native library and a JNI library inside a JAR?

I&#39;ve got some C functions which I am calling through JNI which take a pointer to a structure, and some other functions which will allocate/free a pointer to the same type of structure so that it is a bit easier to deal with my wrapper.  Surprisingly, the JNI documentation says very little about how to deal with C structures.

My C header file looks like so:

    typedef struct _MyStruct {
      float member;
    } MyStruct;

    MyStruct* createNewMyStruct();
    void processData(int *data, int numObjects, MyStruct *arguments);

The corresponding JNI C wrapper file contains:

    JNIEXPORT jobject JNICALL
    Java_com_myorg_MyJavaClass_createNewMyStruct(JNIEnv *env, jobject this) {
      return createNewMyStruct();
    }

    JNIEXPORT void JNICALL
    Java_com_myorg_MyJavaClass_processData(JNIEnv *env, jobject this, jintArray data,
                                           jint numObjects, jobject arguments) {
      int *actualData = (*env)-&gt;GetIntArrayElements(env, data, NULL);
      processData(actualData, numObjects, arguments);
      (*env)-&gt;ReleaseIntArrayElements(env, data, actualData, NULL);
    }

...and finally, the corresponding Java class:

    public class MyJavaClass {
      static { System.loadLibrary(&quot;MyJniLibrary&quot;); }
      
      private native MyStruct createNewMyStruct();
      private native void processData(int[] data, int numObjects, MyStruct arguments);

      private class MyStruct {
        float member;
      }

      public void test() {
        MyStruct foo = createNewMyStruct();
        foo.member = 3.14159f;
        int[] testData = new int[10];
        processData(testData, 10, foo);
      }
    }

Unfortunately, this code crashes the JVM right after hitting `createNewMyStruct()`.  I&#39;m a bit new to JNI and have no idea what the problem could be.

**Edit**: I should note that the C code is very vanilla C, is well-tested and was ported from a working iPhone project.  Also, this project is using the Android NDK framework, which lets you run native C code from an Android project from within JNI.  However, I don&#39;t think that this is strictly an NDK issue... it seems like a JNI setup/initialization error on my part.

How to pass C structs back and forth to Java code in JNI?

I have passed a URL string from Java to C code as `jstring` data type through the use of JNI. And my library method needs a `char *` as url.

 How can I convert `jstring` in `char *` ?


 P.S.: Is there any advantage of using jcharArray in C? (i.e. Passing `char []` instead of string in native method)

JNI converting jstring to char *

What is wrong with my make file?

Android.mk

    LOCAL_PATH := $(call my-dir)
     
    include $(CLEAR_VARS)
    LOCAL_MODULE    := foo
    LOCAL_SRC_FILES := foo.c
    LOCAL_EXPORT_LDLIBS := -llog
    include $(BUILD_SHARED_LIBRARY)

foo.c

    #include &lt;string.h&gt;
    #include &lt;jni.h&gt;
    #include &lt;android/log.h&gt;
    
    #define  LOG_TAG    &quot;foo&quot;
    #define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
     
    void test() {
        LOGI(&quot;test&quot;);
    }

ndk-build

    foo.c:9: undefined reference to `__android_log_print&#39;

undefined reference to `__android_log_print&#39;

I&#39;m looking for a way to easily debug C code in an Android NDK application using Eclipse.  I&#39;ve read ways to debug the app using gdb or something similar but what I want is a way to push messages to Eclipse somehow.

I&#39;m looking for a solution that&#39;s as simple as using a print function in C and seeing it in the DDMS Log or anything similar.  Does anyone have any experience doing this?

Any simple way to log in Android NDK code?

I was surprised to see in the Java source that System.arraycopy is a native method.

Of course the reason is because it&#39;s faster.  But what native tricks is the code able to employ that make it faster?

Why not just loop over the original array and copy each pointer to the new array - surely this isn&#39;t that slow and cumbersome?

Why is System.arraycopy native in Java?

While playing [this puzzle][1] (It&#39;s a Java keyword trivia game), I came across the `native` keyword.

What is the native keyword in Java used for?


  [1]: http://www.sporcle.com/games/robv/java_keywords

What is the native keyword in Java for?

Is it possible to create a native ios app with node.js, and is so does anyone have any examples?

Native IOS app and node.js

Other than the standard `+`, `-`, `*`and `/` operators; but what does these mean (`**` , `^` , `%`, `//`) ?

    &gt;&gt;&gt; 9+float(2) # addition
    11.0
    &gt;&gt;&gt; 9-float(2) # subtraction
    7.0
    &gt;&gt;&gt; 9*float(2) # multiplication
    18.0
    &gt;&gt;&gt; 9/float(2) # division
    4.5
    &gt;&gt;&gt;
    &gt;&gt;&gt; 9**float(2) # This looks like a square, (i.e. power 2) 
    81.0
    &gt;&gt;&gt; 9**float(3) # So ** is equivalent to `math.pow(x,p)` ?
    729.0

**How about the `^` operator?**

    &gt;&gt;&gt; 9^int(2) # What is `^` in `x^u` , it only allows `int` for `u`
    11
    &gt;&gt;&gt; 9^int(3)
    10
    &gt;&gt;&gt; 9^int(4)
    13
    &gt;&gt;&gt; 9^int(5)
    12
    &gt;&gt;&gt; 9^int(6)
    15
    &gt;&gt;&gt; 9^int(7)
    14
    &gt;&gt;&gt; 9^int(8)
    1
    &gt;&gt;&gt; 9^int(9)
    0
    &gt;&gt;&gt; 9^int(10)
    3
    &gt;&gt;&gt; 9^int(11)
    2
    &gt;&gt;&gt; 9^int(12)
    5

**`%` in `x%m` returns a normal remainder modulus, but only if `m &lt; x`, why is that so? What does `%` do?**
 

    &gt;&gt;&gt; 9%float(2)
    1.0
    &gt;&gt;&gt; 9%float(3)
    0.0
    &gt;&gt;&gt; 9%float(4)
    1.0
    &gt;&gt;&gt; 9%float(5)
    4.0
    &gt;&gt;&gt; 9%float(6)
    3.0
    &gt;&gt;&gt; 9%float(7)
    2.0
    &gt;&gt;&gt; 9%float(8)
    1.0
    &gt;&gt;&gt; 9%float(9)
    0.0
    &gt;&gt;&gt; 9%float(10)
    9.0
    &gt;&gt;&gt; 9%float(11)
    9.0
    &gt;&gt;&gt; 9%float(12)
    9.0

**How about the `//` operator? what does it do?**

    &gt;&gt;&gt; 9//float(2)
    4.0
    &gt;&gt;&gt; 9//float(3)
    3.0
    &gt;&gt;&gt; 9//float(4)
    2.0
    &gt;&gt;&gt; 9//float(5)
    1.0
    &gt;&gt;&gt; 9//float(6)
    1.0
    &gt;&gt;&gt; 9//float(7)
    1.0
    &gt;&gt;&gt; 9//float(8)
    1.0
    &gt;&gt;&gt; 9//float(9)
    1.0
    &gt;&gt;&gt; 9//float(1)
    9.0
    &gt;&gt;&gt; 9//float(0.5)
    18.0



What do these operators mean (** , ^ , %, //)?

A native method has the same syntax as an abstract method, but where is it implemented?

 

Content Type	Original Author	Original Content on Stackoverflow
Question	Ben Simmons	View Question on Stackoverflow
Solution 1 - Java	Tom Hawtin - tackline	View Answer on Stackoverflow
Solution 2 - Java	Chris Jester-Young	View Answer on Stackoverflow

Where to find source code for java.lang native methods?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

How to get number of rows inserted by a transaction

Where can I find a list of all the reference implementations for Java EE 6?

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