CORE JAVA - BUG HUNT QUIZ

ganesh@codeops.tech Ganesh Samarthyam

Programmer’s world :)java.lang.NullPointerExceptionat org.eclipse.jface.dialogs.DialogSettings.load(DialogSettings.java:278)at org.eclipse.jface.dialogs.DialogSettings.load(DialogSettings.java:306)at org.eclipse.jface.dialogs.DialogSettings.load(DialogSettings.java:247)at org.eclipse.jface.dialogs.DialogSettings.load(DialogSettings.java:264)at org.eclipse.ui.plugin.AbstractUIPlugin.loadDialogSettings(AbstractUIPlugin.java:411)at org.eclipse.ui.plugin.AbstractUIPlugin.getDialogSettings(AbstractUIPlugin.java:232)at org.eclipse.jdt.internal.ui.JavaPlugin.getDialogSettingsSection(JavaPlugin.java:1012)at org.eclipse.jdt.internal.ui.packageview.PackageExplorerPart.<init>(PackageExplorerPart.java:436)at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)at java.lang.reflect.Constructor.newInstance(Unknown Source)at java.lang.Class.newInstance0(Unknown Source)at java.lang.Class.newInstance(Unknown Source)at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:170)at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:867)at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:51)at org.eclipse.ui.internal.WorkbenchPlugin$1.run(WorkbenchPlugin.java:267)at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:263)at org.eclipse.ui.internal.registry.ViewDescriptor.createView(ViewDescriptor.java:63)at org.eclipse.ui.internal.ViewReference.createPartHelper(ViewReference.java:328)at org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:230)at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:594)at org.eclipse.ui.internal.Perspective.showFastView(Perspective.java:2053)at org.eclipse.ui.internal.Perspective.setActiveFastView(Perspective.java:1835)at org.eclipse.ui.internal.Perspective.setActiveFastView(Perspective.java:1848)at org.eclipse.ui.internal.Perspective.toggleFastView(Perspective.java:2241)at org.eclipse.ui.internal.WorkbenchPage.toggleFastView(WorkbenchPage.java:3824)at org.eclipse.ui.internal.ShowFastViewContribution.showView(ShowFastViewContribution.java:157)at org.eclipse.ui.internal.ShowFastViewContribution.access$1(ShowFastViewContribution.java:155)at org.eclipse.ui.internal.ShowFastViewContribution$3.widgetSelected(ShowFastViewContribution.java:138)at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:228)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:2382)at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2346)at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2198)at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:493)at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:488)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:382)at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)at java.lang.reflect.Method.invoke(Unknown Source)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)

SNAFU!

Question #0

Which browser does this code open?

a) Internet Explorer b) Opera c) FireFox d) Safari

class Google { public static void main(String []args) { http://www.google.com System.out.println("Hello world"); } }

Question #1

Question #2

“95% of the folks out there are completely clueless

about floating-point”

-James Gosling (in 1998 JavaOne keynote address)

Floating-point Numbers are Tricky!

Another Example

class FloatCompare { public static void main(String []args) { double x = 2.0; double y = Math.sqrt(x) ; System.out.println( (y * y) == x); } }

Question #3

Question #4

Which one of the following best describes the behavior of this code?

a) This code segment will give compiler error(s) b) This code segment will return 1 to the caller c) This code segment will return null to the caller d) This code segment will result in throwing a NullPointerException

Question #5class Append { public static void main(String []args) { StringBuffer sb = new StringBuffer('H'); sb.append('i'); System.out.println(sb); } }

Which one of the following best describes the behavior of this code?

a) This code segment will give compiler error(s) b) This code segment will print “Hi” c) This code segment will print “H” d) This code segment will print “i”

Question #6class ReplaceAll { public static void main(String []args) { String date = "18-03-2017" ; String date1 = date.replaceAll( "-" , "." ) ; String date2 = date1.replaceAll( "." , "/" ) ; System.out.println(date2); } }

What is the output of this program?

a) 18-03-2017 b) ---------- c) ………. d) //////////

Question #7

Question #8

Question #9class Base { public Base() { System.out.println("In Base ctor"); } }

class Derived extends Base { public Derived() { System.out.println("In Derived ctor"); } }

class UseArray { public static void main(String []args) { Base [] array = new Derived[2]; array[0] = new Base(); array[1] = new Derived(); } }

Question #10class Stack {

private final int CAPACITY = 100; private Object[] array = new Object[CAPACITY]; private int size = 0;

public void push(Object val) { if (size < CAPACITY)

array[size++] = val; else

throw new StackFullException(); }

public Object pop() { if (size == 0)

throw new StackEmptyException(); else return array[--size];

}}

ganesh@codeops.tech @GSamarthyam

www.codeops.tech slideshare.net/sgganesh

+91 98801 64463 bit.ly/sgganesh