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macOS - How to install Java 17

Could someone please let me know the steps to install Java on a Mac.
I did brew install java
I get this
Warning: openjdk 17.0.1 is already installed and up-to-date.
To reinstall 17.0.1, run:
brew reinstall openjdk
If I do java -version, I get this.
openjdk version "13.0.8" 2021-07-20
If I have navigate to /Library/Java, I have 2 empty directories.
Where is java 17 installed??

In 2023, even if you can use just brew..
brew install openjdk#17
Java will be installed here:
/usr/local/opt/openjdk#17/bin/java
For the system Java wrappers to find this JDK, symlink it with:
sudo ln -sfn /usr/local/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
...give a try to sdkman, it's far better than brew
curl -s "https://get.sdkman.io" | bash
then open a new shell and try list to see what you could install ;-)
sdk list java
At time of writing you could use:
sdk install java 17.0.4.1-tem
Java will be installed here:
/Users/freedev/.sdkman/candidates/java/17.0.4.1-tem

Java doesn't mind if you install multiple versions. This is often required; java is not backwards compatible (it tries to change little, but e.g. the java8 to java9 transition broke a ton of stuff, much of it needless and much of it not reasonably expectable or fixable by libraries and apps, so a bunch of java apps and libraries only run on java8 - just an example).
So, yes, you have installed JDK17. Also, yes, if you just run java without specifying which one you want, you so happen to get java13 here.
To see all installed javas, you can run:
/usr/libexec/java_home -V
to 'override', you can use something like (depends on which shell you're using on your mac):
export JAVA_HOME=`/usr/libexec/java_home -v 17`
(the backticks mean: Run this then take the output of it and treat that as the 'value' of the expression. here, assign it to the JAVA_HOME env var. -v 17 requests a path to java 17. The -V option lists all and is meant for your eyeballs, not for scripts. The -v option is mostly for scripting, and that's how we're using it here).
JAVA_HOME decides which java is used by some things, but the java you get when you just type java is /usr/bin/java, and that executable is actually just a wrapper that picks a java to run from amongst all installed versions. It uses JAVA_HOME to decide which java to actually run. There are wrappers for all the common commands (javac, too). You can always run e.g. which javac to see what that actually runs; you probably see /usr/bin/javac. Everything in /usr/bin is one of these wrapper thingies that looks at JAVA_HOME and then runs the binary it finds there.

To specify version 17
brew install openjdk#17
Later I add create a link:
sudo ln -sfn /usr/local/opt/openjdk#17/libexec/openjdk.jdk \
/Library/Java/JavaVirtualMachines/openjdk-17.jdk
And use jenv to control which java version to use

To used the version installed by homebrew rather than the one installed by the OS you can get detailed information from homebrew by typing
brew info java
Currently it states
For the system Java wrappers to find this JDK, symlink it with
sudo ln -sfn /opt/homebrew/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
openjdk is keg-only, which means it was not symlinked into /opt/homebrew,
because macOS provides similar software and installing this software in
parallel can cause all kinds of trouble.
If you need to have openjdk first in your PATH, run:
echo 'export PATH="/opt/homebrew/opt/openjdk/bin:$PATH"' >> ~/.zshrc
For compilers to find openjdk you may need to set:
export CPPFLAGS="-I/opt/homebrew/opt/openjdk/include"

For Homebrew, the package that installs the new AdoptOpenJDK is named as temurin. So you need to use below command:
brew install --cask temurin17
If you get any error like temurin cask not available then update brew using below commands:
brew update
brew tap homebrew/cask-versions
To switch quickly between different versions of java add the entries in bashrc as per your jdk versions like:
alias j8="export JAVA_HOME=`/usr/libexec/java_home -v 1.8`; java -version"
alias j17="export JAVA_HOME=`/usr/libexec/java_home -v 17`; java -version"

Steps to install
You asked:
let me know the steps to install Java on a Mac.
Download an installer free-of-cost from vendors such as Adoptium, Azul Systems, Bellsoft, Amazon, Oracle, Microsoft, SAP, and others.
Run installer app.
Quit the installer app when done.
Verify installation by typing on a command-line in Terminal.app:java --version
Delete installer app that you downloaded.
Configure your IDE to use that new Java implementation you installed.
Java location
You asked:
Where is java 17 installed??
/Library/Java/JavaVirtualMachines/
In the Finder, choose Go > Go to Folder, and paste /Library/Java/JavaVirtualMachines/.
Note that this is not the Library folder within your home folder. We are not referring to /Users/your_user_name/Library/…. We are referring to the root Library folder that applies across all the user accounts on this Mac.
You said:
I did brew install java
No need for the Homebrew package manager. If you already enjoy using the brew tool, proceed. But if new to Homebrew, skip it if your only goal is to install Java. Just use an installer for Java as you would for many Mac apps.
JavaFX
You added a tag for javafx.
Be aware that for JavaFX, you have two options:
Include the necessary OpenJFX libraries within your development project and within your final app, or …
Use a JDK that includes the JavaFX/OpenJFX libraries.
At least two vendors provide JDK installers that include the JavaFX/OpenJFX libraries:
Azul Systems (ZuluFX)
Bellsoft (LibericaFX)

This answer is specifically if you use Intellij on a Mac
Within IntelliJ, you can use the IDE to add new JDKs of selected versions from common vendors. Instructions for this are here:
Setup the project JDK
When setting up the JDK, you can either:
Select a pre-existing JDK which has been registered with the IDE OR
Use the Add JDK option to add a new JDK which you previously downloaded and installed using the method outlined in Basil's answer OR
Use the Download JDK option to choose a vendor and version of the JDK that the IDE will automatically download, install and make available for selection.
The JDKs installed by Idea will be located in the same location as outlined in Basil's answer for a manual install /Library/Java/JavaVirtualMachines/.
One common issue is that the version of the JDK registered for the project differs from the default version used in the terminal. This can sometimes mean that the app works when run in Idea, then fails when run in the terminal (or, at least that it is executed against a version of the JDK you didn't expect).
To select the version of the JDK to run in the terminal, configure the Java home setting as outlined in rzwitserloot's answer.
export JAVA_HOME=`/usr/libexec/java_home -v 17`
Also, some tools such as the openjfx maven plugin will not use the java version selected in Idea when executing a call to a JDK tool like jlink, but will instead have their own mechanism for finding a JDK to use (e.g. look at JAVA_HOME or use the Maven toolchains plugin). So it is always good to check the JAVA_HOME variable and ensure that it is set to a reasonable value, both for terminal execution and for effective use of Java development tools that may rely on it.

I think that answers here are not fully out of topic, but from my point of view, my case is exactly the same as that of the author. I had already installed java 8, 11, and 13. All of them resides at:
/Library/Java/JavaVirtualMachines/
Nevertheless when I tried to find the path of JDK 17 it resides:
/usr/local/Cellar/openjdk
I use Mac OS Big Sur and the JDK was installed with homebrew

Brew now supports searching old formulae and allowing you to install a specific version. I'm using Homebrew 3.5.2-117-gb941470
Create a local tap: brew tap-new --no-git local/openjdk
Ask Brew to find the formulae of the version you want: brew extract --version 17.0.2 openjdk local/openjdk
Install Java 17 using your new local tap: brew install openjdk#17.0.2
Link the JDK into the MacOS JVM Dir: sudo ln -sfn /usr/local/opt/openjdk#17.0.2/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk17.0.2.jdk
Check Java 17 is available: /usr/libexec/java_home -V
Set Java Home: export JAVA_HOME=$(/usr/libexec/java_home -v17)
Check current version of Java is correct...
$ java --version
openjdk 17.0.2 2022-01-18

The following method installs Java without the need for any additional tools or package managers.
Go to https://jdk.java.net/17/ and download the latest macOS archive.
Download the latest Adoptium release for the Java 17 branch by going to https://adoptium.net/temurin/releases/ and be sure to select the tar.gz version.
The archive is either for x64 (Intel CPU) or for AArch64 (Apple Silicon / M1 CPU).
Then, open a Terminal, and extract the downloaded archive to the system path for Java virtual machines:
cd Downloads
tar xzf OpenJDK17U-jdk_aarch64_mac_hotspot_17.0.5_8.tar.gz -C /Library/Java/JavaVirtualMachines

Confused about JRE and JDK and latest Java versions

On a desktop with a dual boot I currently have Java JDK 8 in the Linux (Mint) system
chris#M17A ~ $ sudo apt install default-jdk
...
default-jdk is already the newest version (2:1.8-56ubuntu2).
...
chris#M17A ~ $ java -version
openjdk version "1.8.0_171"
OpenJDK Runtime Environment (build 1.8.0_171-8u171-b11-0ubuntu0.16.04.1-b11)
OpenJDK 64-Bit Server VM (build 25.171-b11, mixed mode)
But I'm sure that in fact 1.8.0_171 is not the latest version, even of Java 8! If I want to change to 1.11.xxx, which seems to be the latest LTS release (for Oracle non-OpenJDK at least), what should I do? Do I have to manually download something, or use a PPA? How can I be sure my Linux OS is using the version-11 JRE and the version-11 JDK?
I've also never quite understood either about the versioning of the JRE side of things and how this corresponds to the JDK being used. On my Windows machine (W10) I am using a Java 9 JDK but a Java 8 JRE (I think). Is this a bad thing to do?
This question says there is no such thing in Windows as a Java 11 JRE, although there is a Java 11 JDK. Is that a problem in W10? Would it be a bad idea to use an JDK 11 with a JRE 8?
I also simply don't understand why it is not possible read somewhere about the "latest JRE" or "latest stable JRE". These do not appear to be coupled one-to-one with the latest JDK as far as I can make out but I'm having difficulty obtaining clarity about all this.
I also have some difficulty understanding whether I should opt for OpenJDK or the other JDK (they're both Oracle so I don't know how to refer to the non-OpenJDK one... "commercial JDK"?). But unlike the above difficulties there are lots of explanations out there. I am mainly looking for "latest stable release" hopefully with LTS. Seems like "Commercial JDK" version 11 might be the way to go...

Java 8 is the default JDK (recommanded) for your System.
According to this, you need to add the repository of openjdk using this command:
sudo add-apt-repository ppa:openjdk-r/ppa
After that you need to update you index using
sudo apt-get update
If you want to install jdk 11 you can do:
sudo apt-get install openjdk-11-jdk
[Hint]
default-jdk is the default jdk. This means that, if this is up-to-date, you have the recommanded/default version of a jdk.
Also, openjdk seems to be recommanded for linux

How to install openJdk 8 in windows 64 bit os

I need to install open JDK in my Windows 64-bit os. I have used ORACLE open JDK and downloaded from the below link: https://jdk.java.net/8/
While downloading I have selected Accept License Agreement and installed.
But, after the installation when I tried checking the version using command java -version it's showing like regular JDK.
Can anyone help me to get where I went wrong? Or is there any better vendor to install open JDK in windows. Thanks.

Amazon offers an open jdk for Windows (and other OS), but just for Java 8, 11 and 16.
You can download it from here: https://aws.amazon.com/es/corretto/
After installing it and running the java -version command, you will see something like this:
>java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment Corretto-8.242.08.1 (build 1.8.0_242-b08)
OpenJDK 64-Bit Server VM Corretto-8.242.08.1 (build 25.242-b08, mixed mode)

You need to set your java version in environment of you machine and target your JDK8 bin folder, or any JDK that you want to have at your disposal when you run java -version.

The best way to do this is to use the builds from adoptopenjdk. They're very high quality and come in multiple variants for Windows ranging from zip files to MSI installers. Dead simple to install JDK 8, 11 or 15.
But, after the installation when I tried checking the version using command java -version it's showing like regular JDK.
This is because JAVA_HOME is pointing to your old JDK. You need to go to Control Panel and change the Environment Variables. Just do a search on Windows 10 for "Environment Variables" to easily find that configuration panel.

Azul Systems provides builds of OpenJDK and relative installers, for all OSes and JDK versions.
It also provides builds of the JDK with OpenJFX included.
The installers bind JAR files to be executed by Java on Windows.
Download from azul.com website

I know this is old but should anyone run across this in search of OpenJDK 8 go here
https://developers.redhat.com/products/openjdk/download

I had Open JDK 1.7 on CentOS; I installed Oracle's Java rpm; Oracle Java doesn't seem to exist

I started off with CentOS and OpenJDK 1.7
# java -version
java version "1.7.0_25"
OpenJDK Runtime Environment (rhel-2.3.10.4.el6_4-x86_64)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)
In order to run a specific application, I want to use Oracle's Java 1.6, provided from an RPM.
I copied the Oracle binary to a specific new directory:
# pwd
/oracleJava/jdk-6u45-linux-x64-rpm
I extracted the binary and it gave me the following files:
# ls
jdk-6u45-linux-amd64.rpm
sun-javadb-core-10.6.2-1.1.i386.rpm sun-javadb-javadoc-10.6.2-1.1.i386.rpm
sun-javadb-client-10.6.2-1.1.i386.rpm sun-javadb-demo-10.6.2-1.1.i386.rpm
sun-javadb-common-10.6.2-1.1.i386.rpm sun-javadb-docs-10.6.2-1.1.i386.rpm
I installed the RPM and the rpm utility believes that it installed properly:
rpm -q jdk
jdk-1.6.0_45-fcs.x86_64
# rpm -Uvh ./*.rpm
Preparing... ########################################### [100%]
package jdk-2000:1.6.0_45-fcs.x86_64 is already installed
# rpm -Uvh sun-javadb-*.rpm
[I omit the feedback because it generates a formatting error]
#
However, the Java version just shows 1.7
# java -version
java version "1.7.0_25"
OpenJDK Runtime Environment (rhel-2.3.10.4.el6_4-x86_64)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)
In other words, I was expecting the Oracle files to give me some new /java directory somewhere, with a new java executable that would return a different answer for "java -version"
I need that new directory so that I can set JAVA_HOME and use the 1.6 version of Java.
Helpful suggestions would be greatly appreciated. Thanks in advance.

The Oracle JDK RPMs are horrible.
They do not register with the alternatives system.
They do not Provide (in RPM terms) "java"
They have messed up their RPM 'version string' and rely on Epoch (...)
All versions of the JDK (i.e. 1.6 vs 1.7) have the same Epoch
In order to quickly remedy your problem you can run the following:
/usr/sbin/alternatives --install /usr/bin/java java /usr/java/default/bin/java 20000
It will register and prefer the Oracle java installation as an alternative. OpenJDK has weight 16000; here we register with 20000. Once you've run this command you can switch between java versions by using the (already mentioned) alternatives --config java command.
As for a less quick fix you can use my virtual java package. It's quite possibly not perfect (I'm open for improvements ;) ), but it Provides java (making my apache-tomcat package happy) and registers with the alternatives system. This virtual package simply depends on jdk...you can find it here: https://github.com/keystep/virtual-java-rpm

Run the following command to see if your JVM is getting listed.
sudo update-alternatives --config java
If your JVM gets listed select it.

The problem is that Oracle's RPMs are (wilfully IMO!) ignorant of the "alternatives" system.
Instead, they install stuff in a non-standard place (/usr/java) and then expect the user / system administrator to mess with the PATH variable ... by hand.
It is a nuisance!
So what has probably happened in your case is that your JDK / JRE has been installed in a subdirectory of /usr/java ... but since you haven't added the relevant bin subdirectory to the front of your PATH you are still picking up the OpenJDK tools via the java command name.
You can fix this after the fact by using "alternatives" to configure and then select the Oracle commands. But it is messy, especially if you want the JDK tools as well. (There are a lot of them!)

Please check that whether your JAVA_HOME points to JDK 6 using echo $JAVA_HOME. In order change your JAVA_VERSION to Java 6, you need to point to the Java development KIT 6. You also need to add the bin directory to the $PATH variable. Please ensure that JDK6 bin directory comes in the $PATH prior to other JDK bin,if any. You can check the version of your Java in the environment by command java -version.The other answer by learningloop is very perfect to switch between different Java configurations

Try to the following method
delete OpenJDK folder from
/usr/lib/jvm
I had same problem and got solution through this method

Eclipse on Mac 10.8 - Installed 1.7.0 JRE / JDK, but Eclipse won't launch

Installed Java SE 1.7.0u10 from Oracle w/ their installer package
Downloaded and unpacked Eclipse Juno (4.2.1)
Double click Eclipse purple icon and get OS X alert prompt with error message:
To open "Eclipse," you need a Java SE 6 runtime. Would you like to
install one now?
(in terminal) which java - /usr/bin/java
ls -l /usr/bin/java - /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java
(in Finder) Double click eclipse alias (included when unpacked download) - Terminal launches, /Applications/Eclipse/Eclipse.app/Contents/MacOS/eclipse ; exit ; and Exclipse launches without OS X alert prompt.
I've tried modifying the Eclipse app bundle plist to point the -vm key to /System/Library/Frameworks/JavaVM.frameworks/Versions/Current/Commands/java, but I feel like I probably shouldn't have to do this.`
I'd like to know how to get Eclipse to launch by just double clicking on the Application package. It's such a small thing to bug me... :o)

The best answer is to fix the Java 7 installation as shown here :
https://stackoverflow.com/a/19594116
Simple to do and I have confirmed it works on Mavericks. With this fix, you can launch your app from the launchpad as usual. If you upgrade your JDK, you will have to reapply the fix to the new installation.

I had JDK 7 installed and I solved this issue for eclipse Kepler by running eclipse from the terminal instead of the finder.
./eclipse
Just thought to share.
Update 1
For the sake of completeness, if you want to run it from Finder as well, you can wrap the ./eclipse command into a .command file and run it from Finder (so that you don't have to open a terminal)
The following lines should do the job (don't forget to replace "your-full-eclipse-path" with the eclipse path on your machine)
#!/bin/sh
/your-full-eclipse-path/eclipse
After that, give execute permission to the eclipse.command file you just created
chmod +x eclipse.command

I found the answer over on Ask Different
It's an ugly hack, but works perfectly.

posted on this page: Mountain Lion with Java 7 only
To trick OS X to accept Java 7 instead of proposing to install Java 6 a simple symlink is enough:
sudo mkdir /System/Library/Java/JavaVirtualMachines
sudo ln -s /Library/Java/JavaVirtualMachines/1.7.0.jdk /System/Library/Java/JavaVirtualMachines/1.6.0.jdk
Most Java Programs will run with this little hack without the need to install Java 6. OS X's Java Preferences (and maybe some others) will not as it seems to explicitly check the version of the JVM when it is started.
script above can fix my problem.

Hoping you are using 64-bit of Java SE 1.7.0 and so advising the following.
go to Eclipse->Preferences...->Java->Installed JREs
click Add...
Select Standard VM
paste /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home into JRE home
Change the JRE name to something useful like Java SE 7
Click Finish
Check the check-box next to your newly created JRE.
You would need a restart.

For what it's worth, the Eclipse team seems to have worked around it by replacing their dlopen()-based method with a CFBundleCreate()-based one: https://bugs.eclipse.org/bugs/show_bug.cgi?id=411361
In case anybody has the same problem in their code that launches Java and does not want to resort to Apple-only APIs, I found an easier work-around: before dlopen()ing $JRE_HOME/lib/server/libjvm.dylib, make sure to open dlopen() $JRE_HOME/lib/jli/libjli.dylib. Then it won't ask to install Java 6.

Can you imagine that? You have to install a JDK 1.6 to get eclipse ran properly, even if you already have jdk 1.7 installed, and set the JAVA_HOME properly.
To resolve your issue, you just need to download the jdk1.6 from http://support.apple.com/kb/DL1572?viewlocale=en_US, and install it, later you will be able to run eclipse, and you can set the JAVA_HOME to JDK1.7, and you will be able to find the JDK1.7 from eclipse "Preferences".

All these hacks does not work on mac Mavericks,
But a simple and efficient solution is found here
it worked with me like a charm.
Note: a drawback of this solution is when you check your java version using "java -version" command, it will read Java 1.6

open /Library/Java/JavaVirtualMachines/jdkXXXXX.jdk/Contents/Info.plist
settting(<string>BundledApp</string> is usefull!):
<key>JVMCapabilities</key>
<array>
　　<string>JNI</string>
　　<string>BundledApp</string>
　　<string>WebStart</string>
　　<string>Applets</string>
　　<string>CommandLine</string>
</array>

I had the exact same message when setting up a new mac and trying to run eclipse 4.2.2 with only Java SE 7 installed (as part of JDK 7u17).
In order to be able to successfully launch Eclipse I had to let OSX download and install Apple's Java SE 6 runtime first before installing the latest JDK.
After installing the JDK, the command java -version correctly shows:
java version "1.7.0_17"
Java(TM) SE Runtime Environment (build 1.7.0_17-b02)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)
Trying to solve the problem the other way around didn't work -- i.e. installing JDK 7u17 first before installing Java SE 6 as suggested in the message.

I had the exactly same problem some days ago and I solved it today. Just installed this http://support.apple.com/kb/dl1572
And after that, when I opened the eclipse the OSX installed some java update and opening eclipse by Eclipse.app started working.
Hope it works with you too.

If you'd like to install Java 6 JDK only (no Java 7 JDK/JRE, no Java 6 JRE only), install the Apple OSX Java DMG (at time of writing, this was http://adcdownload.apple.com/Developer_Tools/java_for_os_x_2013003_developer_package/java_for_os_x_2013003_dp__11m4406.dmg).
You still won't be able to start Eclipse. Make a directory JavaVirtualMachines under /System/Library/Java. And then make an Alias of the java version folder at /Library/Java/JavaVirtualMachines and rename the alias 1.6.0.jdk and copy that alias to /System/Library/Java/JavaVirtualMachines/
After finished, you will have an Alias at /System/Library/Java/JavaVirtualMachines/1.6.0.jdk that points to the Java install directory at */Library/Java/JavaVirtualMachines/1.6.0_XX-XXX-XXX.jdk*

Install latest JDK from Sun, it installs into /Library/Java/JavaVirtualMachines/, e.g. /Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk
sudo mkdir /System/Library/Java/JavaVirtualMachines
sudo ln -s /Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk/ /System/Library/Java/JavaVirtualMachines/1.6.0.jdk
========= this trick used to work on Mountain Lion, but not on Maverick 10.9 somehow ============
Tried this again on Maverick, it does not work anymore. I also tried to change eclipse app plist and eclipse.ini (by adding -vm or ), does not work either.
Some people suggested that this is caused by Eclipse binary prepared using Apple 1.6 appbundler instead of Oracle java7 appbundler: Application is using Java 6 from Apple instead of Java 7 from Oracle on Mac OS X?
For now, please just type the eclipse from command line, which works fine with JAVA_HOME set to Java 7 (/usr/libexec/java_home command will tell you)

How to Make Eclipse Run on OS X 10.9 Mavericks
Attempting to launch various Eclipse versions after the Mavericks upgrade pops up a dialog with this message:
To open "Eclipse.app" you need a Java SE 6 runtime. Would you like to install one now?
It turns out that Java 7 is disabled by default in OS X 10.9.
This is easily verified as follows:
$ java --version
No Java runtime present, requesting install.
The solution is to install the latest supported Java version from Apple support: Java for OS X 2013-005 (http://support.apple.com/kb/DL1572)
As of 10/15/13 this would be Java SE 6 1.6.0_65.
Post Date: Oct 15, 2013
File Size: 63.98 MB
After the install, Eclipse will run as expected from the Dock, the Finder, or the Terminal without any tricks, hacks, or work-arounds.

I wanted to run Eclipse itself with Java 7. As I have a couple of plugins that do not work without it. For me neither solution worked for 10.9, but I found a workaround. The main idea is that you start eclipse with java -jar launcher.jar and provide a couple of magic properties and then it starts. This guy provided the command line script in comments that works for me:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=411361#c25

I found the same problem (Mac OS X 10.9.2, Java 1.7.0_53b13, Eclipse Kepler). The workaround was quite easy:
Find the executable in Finder (CMD+Click on Eclipse's icon in the Dock)
Remove the icon from the Dock
CTRL+Click on the executable in Finder
ALT+Open (to allow the execution of a non-signed application)
Eclipse opens normally and without any problem
Re-dragged the program onto the Dock

I had this problem and found that I did not have JDK installed on my Mac. Once I did that, Eclipse starts normally.

I had same problem.
First of all ; JDK(java development Kit) and JRE(Java Runtime Environment) are different things. It was confused by people
In order to install eclipse yo should install latest JDK . So
Visit
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
Download suitable version for your mac
You can check your version now ; it won't be 1.6 anymore
Try to install eclipse again , see it works.
Good luck!..