Java


JavaFX: Could not execute Jar build from artifact, while we could execute from IntelliJ IDEA

One of the applications we recently build on IntelliJ IDEA was using JavaFX.

When executing the application from inside IntelliJ, it would work as expected and load the GUI.
On the other hand, when executing the jar file from the terminal, we would get the following error:

$ java -jar hello.jar 
Graphics Device initialization failed for :  es2, sw
Error initializing QuantumRenderer: no suitable pipeline found
java.lang.RuntimeException: java.lang.RuntimeException: Error initializing QuantumRenderer: no suitable pipeline found
	at com.sun.javafx.tk.quantum.QuantumRenderer.getInstance(QuantumRenderer.java:280)
	at com.sun.javafx.tk.quantum.QuantumToolkit.init(QuantumToolkit.java:221)
	at com.sun.javafx.tk.Toolkit.getToolkit(Toolkit.java:205)
	at com.sun.javafx.application.PlatformImpl.startup(PlatformImpl.java:209)
	at com.sun.javafx.application.LauncherImpl.startToolkit(LauncherImpl.java:675)
	at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:337)
	at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Error initializing QuantumRenderer: no suitable pipeline found
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.init(QuantumRenderer.java:94)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:124)
	at java.lang.Thread.run(Thread.java:745)
Exception in thread "main" java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: No toolkit found
	at com.sun.javafx.tk.Toolkit.getToolkit(Toolkit.java:217)
	at com.sun.javafx.application.PlatformImpl.startup(PlatformImpl.java:209)
	at com.sun.javafx.application.LauncherImpl.startToolkit(LauncherImpl.java:675)
	at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:337)
	at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
	... 5 more

As the above information was not very helpful, we executed the jar again using the -Dprism.verbose=true directive to get more information from the error.

$ java -Dprism.verbose=true -jar hello.jar 
Prism pipeline init order: es2 sw 
Using java-based Pisces rasterizer
Using dirty region optimizations
Not using texture mask for primitives
Not forcing power of 2 sizes for textures
Using hardware CLAMP_TO_ZERO mode
Opting in for HiDPI pixel scaling
Prism pipeline name = com.sun.prism.es2.ES2Pipeline
Loading ES2 native library ... prism_es2
GraphicsPipeline.createPipeline failed for com.sun.prism.es2.ES2Pipeline
java.lang.UnsatisfiedLinkError: Can't load library: /home/user/Projects/Java/hello/out/artifacts/amd64/libprism_es2.so
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1827)
	at java.lang.Runtime.load0(Runtime.java:809)
	at java.lang.System.load(System.java:1086)
	at com.sun.glass.utils.NativeLibLoader.loadLibraryFullPath(NativeLibLoader.java:201)
	at com.sun.glass.utils.NativeLibLoader.loadLibraryInternal(NativeLibLoader.java:94)
	at com.sun.glass.utils.NativeLibLoader.loadLibrary(NativeLibLoader.java:39)
	at com.sun.prism.es2.ES2Pipeline.lambda$static$0(ES2Pipeline.java:68)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.prism.es2.ES2Pipeline.(ES2Pipeline.java:50)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.sun.prism.GraphicsPipeline.createPipeline(GraphicsPipeline.java:187)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.init(QuantumRenderer.java:91)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:124)
	at java.lang.Thread.run(Thread.java:745)
*** Fallback to Prism SW pipeline
Prism pipeline name = com.sun.prism.sw.SWPipeline
GraphicsPipeline.createPipeline failed for com.sun.prism.sw.SWPipeline
java.lang.UnsatisfiedLinkError: Can't load library: /home/user/Projects/Java/hello/out/artifacts/amd64/libprism_sw.so
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1827)
	at java.lang.Runtime.load0(Runtime.java:809)
	at java.lang.System.load(System.java:1086)
	at com.sun.glass.utils.NativeLibLoader.loadLibraryFullPath(NativeLibLoader.java:201)
	at com.sun.glass.utils.NativeLibLoader.loadLibraryInternal(NativeLibLoader.java:94)
	at com.sun.glass.utils.NativeLibLoader.loadLibrary(NativeLibLoader.java:39)
	at com.sun.prism.sw.SWPipeline.lambda$static$0(SWPipeline.java:42)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.prism.sw.SWPipeline.(SWPipeline.java:41)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.sun.prism.GraphicsPipeline.createPipeline(GraphicsPipeline.java:187)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.init(QuantumRenderer.java:91)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:124)
	at java.lang.Thread.run(Thread.java:745)
Graphics Device initialization failed for :  es2, sw
Error initializing QuantumRenderer: no suitable pipeline found
java.lang.RuntimeException: java.lang.RuntimeException: Error initializing QuantumRenderer: no suitable pipeline found
	at com.sun.javafx.tk.quantum.QuantumRenderer.getInstance(QuantumRenderer.java:280)
	at com.sun.javafx.tk.quantum.QuantumToolkit.init(QuantumToolkit.java:221)
	at com.sun.javafx.tk.Toolkit.getToolkit(Toolkit.java:205)
	at com.sun.javafx.application.PlatformImpl.startup(PlatformImpl.java:209)
	at com.sun.javafx.application.LauncherImpl.startToolkit(LauncherImpl.java:675)
	at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:337)
	at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Error initializing QuantumRenderer: no suitable pipeline found
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.init(QuantumRenderer.java:94)
	at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:124)
	at java.lang.Thread.run(Thread.java:745)
Exception in thread "main" java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: No toolkit found
	at com.sun.javafx.tk.Toolkit.getToolkit(Toolkit.java:217)
	at com.sun.javafx.application.PlatformImpl.startup(PlatformImpl.java:209)
	at com.sun.javafx.application.LauncherImpl.startToolkit(LauncherImpl.java:675)
	at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:337)
	at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
	... 5 more

From the new log, we could see that the application was trying to load some .so (libprism_es2.so and libprism_sw.so) files that were not available in LD_LIBRARY_PATH.
We used find, to locate them:

find / -name "libprism_es2.so" 2>/dev/null;

Then we updated the LD_LIBRARY_PATH variable to include the new path

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/idea-IC/jre64/lib/amd64/;

java -jar hello.jar;

Note: Here we used the copies that were available in our IntelliJ IDEA installation.
It is not recommended as you need to deploy them per machine, but in our case it was OK as the development machine was the actual machine to use the tool as well.


Creating Jar with Intellij IDEA 2017.3 – no main manifest attribute, in .jar

Recently we tried to create a Jar file from IntelliJ IDEA 2017.3 using Maven.

After building the artifact, we got the error no main manifest attribute, in $FILE.jar while executing the jar file created by IntelliJ.
After extracting the jar we observed that there was a manifest file but not the one that was specified while creating the artifact.

After some serious google-fu, we got to the following bug ticket.
Apparently, IntelliJ does not read the manifest file that is located in the src/main/java folder!
Working Solution: As suggested in the ticket, we moved the META-INF folder to src/main/resources and rebuild the artifact.

 


Fedora install JDK (OpenJDK) 2

As we were setting up a machine that would be used for software development, we came to the need of installing a Java Development Kit (JDK).
There are two popular choices on the web between the OpenJDK and the Oracle JDK, we decided to go with the OpenJDK option which is a free and open source implementation of the Java Platform and it is part of the official Fedora repositories.

To install the OpenJDK along with all the needed libraries for development we used the following command:

sudo dnf install java-1.8.0-openjdk java-1.8.0-openjdk-devel;

On our GNU/Linux Fedora the installation folder of the JDK was /usr/lib/jvm/java-1.8.0-openjdk.

 


Remove all non digit characters from String

The following Java snippet removes all non-digit characters from a String.
Non-digit characters are any characters that are not in the following set [0, 1, 2, 3, 4 ,5 ,6 ,7 ,8, 9].

myString.replaceAll("\\D", "");

For a summary of regular-expression constructs and information on the character classes supported by Java pattern visit the following link.

The \\D pattern that we used in our code is a predefined character class for non-digit characters. It is equivalent to [^0-9]that negates the predefined character class for digit characters [0-9].


Java: remove leading character (or any prefix) from String only if it matches

The following snippet allows you to check if a String in Java starts with a specific character (or a specific prefix) that you are looking for and remove it.
To keep the number of lines small, we used the Java ?: ternary operator, which defines a conditional expression in a compact way.
Then, to quickly check if the first character(s) is the one we are looking for before removing it we used the String.startsWith().
To compute the number of characters to remove we used the String.length() on the needle.
Finally, to strip the leading character(s) we used String.substring() whenever the prefix matched.

final String needle = "//";
final int needleSize = needle.length();
String haystack = "";
haystack = haystack.startsWith(needle) ? haystack.substring(needleSize) : haystack;
System.out.print(haystack);

haystack = "apple";
haystack = haystack.startsWith(needle) ? haystack.substring(needleSize) : haystack;
System.out.println(haystack);

haystack = "//banana";
haystack = haystack.startsWith(needle) ? haystack.substring(needleSize) : haystack;
System.out.println(haystack);

The above code will result in the following:

apple
banana

 

Bonus: to remove all the instances of a character anywhere in a string:

final String needle = "a";
final int needleSize = needle.length();
String haystack = "banana";
haystack = haystack.replace(needle,"");
System.out.println(haystack);

The above code will result in the following:

bnn

Bonus: to remove the first instance of a character anywhere in a string:

final String needle = "a";
final int needleSize = needle.length();
String haystack = "banana";
haystack = haystack.replaceFirst(needle,"");
System.out.println(haystack);

The above code will result in the following:

bnana

Java: Methods on how to iterate over a List

Following we present a few methods on how to iterate over a List in Java.

Currently we present:

  1. Using a standard for loop
  2. Using an iterator to loop
  3. Using a For-Each loop
  4. Using Streams
ListLooper.java (compressed) (0 downloads)
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

public class ListLooper {

    public static void main(final String[] argv) {

        final String elementsArray[] = new String[] { "First Element", "Second Element", "Third Element" };
        // First of all we convert an array of Strings to a list of Strings, we do this to avoid adding each element to the list we will use by using the add() method.
        final List<String> elementsList = Arrays.asList(elementsArray);

        // Method 1: Using a standard for loop
        System.out.println("Method 1: Using a standard for loop");
        // We will loop N times, where N is the size of the list.
        // Since the first element of the list is on position 0, we start from that and finish at position N-1.
        for (int i = 0; i < elementsList.size(); i++) {

            // Using get() we retrieve the element at position.
            System.out.println(elementsList.get(i));
        }

        // Method 2: Using an iterator to loop
        System.out.println("Method 2: Using an iterator to loop");
        // The Java iterator is an interface that belongs to the collection framework and allows us to traverse a collection and access the data element of the collection without bothering the user about the implementation details of that collection. 
        final Iterator<String> iterator = elementsList.iterator();
        while (iterator.hasNext()) {

            // next() returns the next element in the collection until the hasNext() method returns false.
            System.out.println(iterator.next());
        }

        // Method 3: Using a For-Each loop
        System.out.println("Method 3: Using a For-Each loop");
        // This code works for any object that implements the Iterable interface.
        for (final String element : elementsList) {

            System.out.println(element);
        }

        // Method 4: Using Streams
        System.out.println("Method 4: Using Streams");
        // This code will not work for Java versions earlier than Java 8.
        elementsList.forEach((element) -> {

            System.out.println(element);
        });
     }
}
ListLooper.java (compressed) (0 downloads)

Compilation and execution are presented in the next section.

javac ListLooper.java;

java ListLooper;
Method 1: Using a standard for loop
First Element
Second Element
Third Element
Method 2: Using an iterator to loop
First Element
Second Element
Third Element
Method 3: Using a For-Each loop
First Element
Second Element
Third Element
Method 4: Using Streams
First Element
Second Element
Third Element

Following is the Java version used in this article

java -version
openjdk version "1.8.0_111"
OpenJDK Runtime Environment (build 1.8.0_111-b16)
OpenJDK 64-Bit Server VM (build 25.111-b16, mixed mode)

Java: Automatically get Enum from String

The following code will create a static map that contains entries where the key would be the string representation of the enum enum.toString() and value would be the enum itself. This way you can retrieve an enum from its string representation using the static fromString() method.

public enum Type {

    ACCOUNT,
    CLIENT;

    public static Type fromString(final String name) {

        final Type element = sMap.get(name);
        if (element != null) {

            return element;
        }
        throw new IllegalArgumentException(String.format("Unknown value: <%s> for %s", name, Type.class.toString()));
    }

    private static final Map<String, Type> sMap = new HashMap<>();

    static {
        for (final Type t : Type.values()) {

            sMap.put(t.toString(), t);
        }
    }
}

For a more general solution, please checkout https://bytefreaks.net/programming-2/java/java-create-a-lookup-table-for-an-enum, that post will show you how to create a lookup table for any type of value (in contrast to using the enum.toString() method)


Java: Create a lookup table for an Enum 4

Simple Enum

Assuming the user has a simple enum that does not have any member variable as follows:

public enum Grades {
    A, B, C, D, E, F
}

In this case, we do not need to create a map to get an enum value from an input string. We can use the enum build-in method valueOf which returns the enum constant of the specified enum type with the specified name.

Please note that the input string must match exactly an identifier used to declare an enum constant in this type. Extraneous white-space characters or wrong letter case are not permitted.

An Enum that has a member variable

Switching to a more interesting example, we assume the user has an enum type that each enum constant has a member variable. In the following example each constant has an int value as member.

public enum Weekday {

    MONDAY(1),
    TUESDAY(2),
    WEDNESDAY(3),
    THURSDAY(4),
    FRIDAY(5),
    SATURDAY(6),
    SUNDAY(7);

    public int getCode() {

        return mCode;
    }

    Weekday(final int code) {

        mCode = code;
    }

    private final int mCode;
}

In this example, getting the matching enum constant for an input integer number is not as straight forward as before. We could iterate over all constants check their code and return the one that matches but that would not be efficient, especially for enum types that have many constants.

What we propose is to create a static map of elements that will have on the key part the value of the enum constant and on the value part the actual enum constant.

public enum Weekday {

    MONDAY(1),
    TUESDAY(2),
    WEDNESDAY(3),
    THURSDAY(4),
    FRIDAY(5),
    SATURDAY(6),
    SUNDAY(7);

    public int getCode() {

        return mCode;
    }

    public static Weekday fromCode(final int code) {

        final Weekday element = sMap.get(code);
        if (element != null) {

            return element;
        }
        throw new IllegalArgumentException(String.format("Unknown code: <%d> for %s", code, Weekday.class.toString()));
    }

    Weekday(final int code) {

        mCode = code;
    }

    private static final Map<Integer, Weekday> sMap = new HashMap<>();

    static {
        for (final Weekday d : Weekday.values()) {

            sMap.put(d.getCode(), d);
        }
    }
    private final int mCode;
}

What we did in the above code, was to statically create the map we described. Which is, a map from the value that each enum constant holds to the constant. Then using the fromCode method we defined, we check the map for the input value, if the value is not part of the keys set of the map, it will throw an Illegal Argument Exception.

Doing Even better

An improvement we could do in the above code, would be to extract the part of the code that iterates over the fields and creates the map to reuse it. To do that, we need to use Functional Interface. Meaning we will create a function that takes as input another function that expects some input (if any) and produces as output an element of the type of the key.

Our function that can be used for all enums that their constants hold an int value is the following:

//ToIntFunction represents a function that produces an int-valued result. This is the int-producing primitive specialization for Function. This is a functional interface whose functional method is applyAsInt(Object).
public static <E extends Enum<E>> Map<Integer, E> createMap(final ToIntFunction<E> converter, final Class<E> enumClass) {

    final Map<Integer, E> map = new HashMap<>();
    for (final E s : enumClass.getEnumConstants()) {

        map.put(converter.applyAsInt(s), s);
    }
    return map;
}

The code of the enum could change to the following:

public enum Weekday {

    MONDAY(1),
    TUESDAY(2),
    WEDNESDAY(3),
    THURSDAY(4),
    FRIDAY(5),
    SATURDAY(6),
    SUNDAY(7);

    public int getCode() {

        return mCode;
    }

    public static Weekday fromCode(final int code) {

        final Weekday element = sMap.get(code);
        if (element != null) {

            return element;
        }
        throw new IllegalArgumentException(String.format("Unknown code: <%d> for %s", code, Weekday.class.toString()));
    }

    Weekday(final int code) {

        mCode = code;
    }

    private static final Map<Integer, Weekday> sMap = Collections.unmodifiableMap(createMap(Weekday::getCode, Weekday.class));

    private final int mCode;
}

The function that we used as input to the new function is the getCode we defined in the enum. As you can see, it is a function that produces an int-valued result just as the requirement of the ToIntFunction parameter asks for.


Java: Breakdown a long number to the powers of two it is composed from 1

The following function will accept a long number as input and will produce an LongStream, which is a sequence of primitive long-valued elements that supports sequential and parallel aggregate operations.

public static LongStream splitToPowersOfTwo(final long input) {

    long temp = input;
    final LongStream.Builder builder = LongStream.builder();

    while (temp != 0) {

        //Long.lowestOneBit: Finds the lowest-order ("rightmost") one-bit in the specified long value and returns a long number that has only the bit in the previously matched position set as 1. This value is a power of two that is one of the components of the number. If the number is zero, the function returns zero.
        final long powerOfTwo = Long.lowestOneBit(temp);
        builder.add(powerOfTwo);
        //We update our temp by subtracting the number we got, our goal is to remove the previously matched bit and get the next one on the next iteration.
        temp = temp & ~ powerOfTwo;
    }

    return builder.build();
}

We used Long.lowestOneBit as it makes it easy for us to breakdown the number to its power of two components by matching for us only one bit at time.

Example of usage:

Scenario: We want to breakdown a long number to the powers of two that their sum produces the number and create a String with those values. Using our function, we can do the following:

final String output = splitToPowersOfTwo(flags).mapToObj(Long::toString).collect(Collectors.joining(", "));

Note: an LongStream is not the same as a Stream<Long>, we used .mapToObj(Long::toString) which calls the static method Long.toString(long). This is different to calling .map(Long::toString) on a Stream<Long> as the latter won’t compile because it is ambiguous.