Java optional parameters

2021-6-3 anglehua

How do I use optional parameters in Java? What specification supports optional parameters? varargs could do that (in a way). Other than that, all variables in the declaration of the method must be supplied. If you want a variable to be optional, you can overload the method using a signature which ...

阅读全文>>

评论(0) 浏览(108)

Error java.lang.OutOfMemoryError: GC overhead limit exceeded

2021-6-3 anglehua

I get this error message as I execute my JUnit tests: java.lang.OutOfMemoryError: GC overhead limit exceeded I know what an OutOfMemoryError is, but what does GC overhead limit mean? How can I solve this? This message means that for some reason the garbage collector is taking an excessive amount o...

阅读全文>>

评论(0) 浏览(102)

How to convert a char to a String?

2021-6-3 anglehua

I have a char and I need a String. How do I convert from one to the other? You can use Character.toString(char). Note that this method simply returns a call to String.valueOf(char), which also works. As others have noted, string concatenation works as a shortcut as well: String s = "" + 's'; But t...

阅读全文>>

评论(0) 浏览(99)

Efficiency of Java “Double Brace Initialization”?

2021-6-3 anglehua

In Hidden Features of Java the top answer mentions Double Brace Initialization, with a very enticing syntax: Set<String> flavors = new HashSet<String>() {{ add("vanilla"); add("strawberry"); add("chocolate"); add("butter pecan"); }}; This idiom creates an anonymous inner...

阅读全文>>

评论(0) 浏览(123)

How do I join two lists in Java?

2021-6-3 anglehua

Conditions: do not modify the original lists; JDK only, no external libraries. Bonus points for a one-liner or a JDK 1.3 version. Is there a simpler way than: List<String> newList = new ArrayList<String>(); newList.addAll(listOne); newList.addAll(listTwo); In Java 8: List<String>...

阅读全文>>

评论(0) 浏览(93)

What is the difference between JSF, Servlet and JSP?

2021-6-3 anglehua

I have some questions. These are : How are JSP and Servlet related to each other? Is JSP some kind of Servlet? How are JSP and JSF related to each other? Is JSF some kind of Pre-Build UI based JSP like ASP.NET-MVC? JSP (JavaServer Pages) JSP is a Java view technology running on the server machi...

阅读全文>>

评论(0) 浏览(106)

Linking to an external URL in Javadoc?

2021-6-3 anglehua

Something like: /** * See {@linktourl http://google.com} */ This creates a "See Also" heading containing the link, i.e.: /** * @see <a href="http://google.com">http://google.com</a> */ will render as: See Also:            http://google.com whereas this: /** * See <a href="...

阅读全文>>

评论(0) 浏览(127)

What is difference between CrudRepository and JpaRepository interfaces in Spring Data JPA?

2021-6-3 anglehua

What is the difference between CrudRepository and JpaRepository interfaces in Spring Data JPA? When I see the examples on the web, I see them there used kind of interchangeably. What is the difference between them? Why would you want to use one over the other? JpaRepository extends PagingAndSortin...

阅读全文>>

评论(0) 浏览(92)

How do I copy an object in Java?

2021-6-3 anglehua

Consider the code below: DummyBean dum = new DummyBean(); dum.setDummy("foo"); System.out.println(dum.getDummy()); // prints 'foo' DummyBean dumtwo = dum; System.out.println(dumtwo.getDummy()); // prints 'foo' dum.setDummy("bar"); System.out.println(dumtwo.getDummy()); // prints 'bar' but it shoul...

阅读全文>>

评论(0) 浏览(102)

What is the Java equivalent for LINQ?

2021-6-3 anglehua

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago. ...

阅读全文>>

评论(0) 浏览(141)

What is a daemon thread in Java?

2021-6-3 anglehua

Can anybody tell me what daemon threads are in Java? A daemon thread is a thread that does not prevent the JVM from exiting when the program finishes but the thread is still running. An example for a daemon thread is the garbage collection. You can use the setDaemon(boolean) method to change the Th...

阅读全文>>

评论(0) 浏览(80)

What's the difference between SoftReference and WeakReference in Java?

2021-6-3 anglehua

What's the difference between java.lang.ref.WeakReference and java.lang.ref.SoftReference ? From Understanding Weak References, by Ethan Nicholas: Weak references A weak reference, simply put, is a reference that isn't strong enough to force an object to remain in memory. Weak references all...

阅读全文>>

评论(0) 浏览(119)

How to pass an object from one activity to another on Android

2021-6-3 anglehua

I am trying to work on sending an object of my customer class from one Activity and display it in another Activity. The code for the customer class: public class Customer { private String firstName, lastName, Address; int Age; public Customer(String fname, String lname, int age, String...

阅读全文>>

评论(0) 浏览(104)

What is an efficient way to implement a singleton pattern in Java?

2021-6-3 anglehua

Closed. This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 2 years ago. ...

阅读全文>>

评论(0) 浏览(112)

Access restriction on class due to restriction on required library rt.jar?

2021-6-3 anglehua

I'm attempting to compile Java 1.4 code that was created by IBM's WSDL2Java on Java5 without recreating the stubs and saw this error in Eclipse. I'm under the assumption that the stubs generated should just compile as long as the runtime jars are available (they are). Access restriction: The type QN...

阅读全文>>

评论(0) 浏览(102)

Unfortunately MyApp has stopped. How can I solve this?

2021-6-3 anglehua

I am developing an application, and everytime I run it, I get the message: Unfortunately, MyApp has stopped. What can I do to solve this? About this question - obviously inspired by What is a stack trace, and how can I use it to debug my application errors?, there are lots of questions stating th...

阅读全文>>

评论(0) 浏览(106)

How do I tell Maven to use the latest version of a dependency?

2021-6-3 anglehua

In Maven, dependencies are usually set up like this: <dependency> <groupId>wonderful-inc</groupId> <artifactId>dream-library</artifactId> <version>1.2.3</version> </dependency> Now, if you are working with libraries that have frequent releases, ...

阅读全文>>

评论(0) 浏览(162)

File to byte[] in Java

2021-6-3 anglehua

How do I convert a java.io.File to a byte[]? It depends on what best means for you. Productivity wise, don't reinvent the wheel and use Apache Commons. Which is here FileUtils.readFileToByteArray(File input). From JDK 7 you can use Files.readAllBytes(Path). Example: import java.io.File; import jav...

阅读全文>>

评论(0) 浏览(101)

How to make a new List in Java

2021-6-3 anglehua

We create a Set as: Set myset = new HashSet() How do we create a List in Java? List myList = new ArrayList(); or with generics (Java 7 or later) List<MyType> myList = new ArrayList<>(); or with generics (Old java versions) List<MyType> myList = new ArrayList<MyType>(); ...

阅读全文>>

评论(0) 浏览(134)

How to call a method after a delay in Android

2021-6-3 anglehua

I want to be able to call the following method after a specified delay. In objective c there was something like: [self performSelector:@selector(DoSomething) withObject:nil afterDelay:5]; Is there an equivalent of this method in android with java? For example I need to be able to call a method aft...

阅读全文>>

评论(0) 浏览(73)

Powered by emlog 京ICP备15036472号-3 sitemap