Java – How to open Java project in Eclipse plugin

eclipse-pluginjava

I used the following code to get IJavaProject type from string:

IProject project = ResourcesPlugin.getWorkspace().getRoot().getProject(projectName);
IJavaProject javaProject = JavaCore.create(project);

After this, I used javaProject.open(monitor); where monitor is of type IProgreeMonitor, to open the project… I am not able to open the filr there is some problem with it. The exception shown is:

Java Model Exception: Java Model Status [com.ibm.plugin does not exist]
 at org.eclipse.jdt.internal.core.JavaElement.newJavaModelException(JavaElement.java:501)
 at org.eclipse.jdt.internal.core.Openable.generateInfos(Openable.java:245)
 at org.eclipse.jdt.internal.core.JavaElement.openWhenClosed(JavaElement.java:514)
 at org.eclipse.jdt.internal.core.JavaElement.getElementInfo(JavaElement.java:251)
 at org.eclipse.jdt.internal.core.Openable.open(Openable.java:431)
 at packagesearch.HelloWorldAction.run(HelloWorldAction.java:49)
 at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:251)
 at org.eclipse.ui.internal.WWinPluginAction.runWithEvent(WWinPluginAction.java:229)
 at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:583)
 at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:500)
 at org.eclipse.jface.action.ActionContributionItem$6.handleEvent(ActionContributionItem.java:452)
 at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
 at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
 at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3823)
 at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3422)
 at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2384)
 at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2348)
 at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2200)
 at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:495)
 at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
 at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:490)
 at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
 at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
 at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:193)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:386)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 at java.lang.reflect.Method.invoke(Method.java:599)
 at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:549)
 at org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
 at org.eclipse.equinox.launcher.Main.run(Main.java:1236)
 at org.eclipse.equinox.launcher.Main.main(Main.java:1212)

Best Answer

As mentioned in my previous answer, your project does not exist, meaning you are trying to open 'null'.

Hence the exception.

Related Solutions

Java – Is Java “pass-by-reference” or “pass-by-value”

Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners.

It goes like this:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

    // we pass the object to foo
    foo(aDog);
    // aDog variable is still pointing to the "Max" dog when foo(...) returns
    aDog.getName().equals("Max"); // true
    aDog.getName().equals("Fifi"); // false
    aDog == oldDog; // true
}

public static void foo(Dog d) {
    d.getName().equals("Max"); // true
    // change d inside of foo() to point to a new Dog instance "Fifi"
    d = new Dog("Fifi");
    d.getName().equals("Fifi"); // true
}

In the example above aDog.getName() will still return "Max". The value aDog within main is not changed in the function foo with the Dog "Fifi" as the object reference is passed by value. If it were passed by reference, then the aDog.getName() in main would return "Fifi" after the call to foo.

Likewise:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

    foo(aDog);
    // when foo(...) returns, the name of the dog has been changed to "Fifi"
    aDog.getName().equals("Fifi"); // true
    // but it is still the same dog:
    aDog == oldDog; // true
}

public static void foo(Dog d) {
    d.getName().equals("Max"); // true
    // this changes the name of d to be "Fifi"
    d.setName("Fifi");
}

In the above example, Fifi is the dog's name after call to foo(aDog) because the object's name was set inside of foo(...). Any operations that foo performs on d are such that, for all practical purposes, they are performed on aDog, but it is not possible to change the value of the variable aDog itself.

For more information on pass by reference and pass by value, consult the following SO answer: https://stackoverflow.com/a/430958/6005228. This explains more thoroughly the semantics and history behind the two and also explains why Java and many other modern languages appear to do both in certain cases.

Java – How to efficiently iterate over each entry in a Java Map

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

On Java 10+:

for (var entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

Best Answer

Related Solutions

Java – Is Java “pass-by-reference” or “pass-by-value”

Java – How to efficiently iterate over each entry in a Java Map

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