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Resolve OutOfMemoryError With ExcelExport : Export Excel Utility with Apache POI Stream API (SXSSF)

                                 Whenever we try to export excel of huge data (for ex: around 200000-300000 records), most of the time we end up with OutOfMemoryError:JavaHeapSpace. And also consuming more time to process or export that much of data. Main reason to this kind of problem is that, the prior version of Apache POI (prior to 3.8) will not provide proper solution for this kind of situations and also we have other issues with the API designed with those versions. Even I had faced issues of not supporting more than 65000 rows of data during exporting excel with prior versions of POI. But with the version 3.8 and higher they come with solutions for all these problems. To resolve Memory issue and performance issue of Excel Export they have utilized stream API to design their API to support huge data export and performance issues. With stream API we can flush only few rows of data into the Memory and reamining we can flush to the hard memory (permanent Memory). In this examp
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How To Resolve "Java compiler level does not match the version of the installed Java project facet." Issue in Eclipse, STS tool or Eclipse Based Tools

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                  I have faced this issue during the Java 7 upgrade from Java 6 into one of our application. You will face this issue suppose if your application or project built on lower versions of Java (in my case it is Java 1.6) and you are trying to upgrade it to the Higher versions of Java (in My case it is Java 1.7), then Eclipse will throw this error in the tool. You will face this error even after changing the compiler version from build path. To fix this issue Follow the Below Mentioned Steps. 1.  Open the ' Markers ' Tab at the bottom of the eclipse or STS tool beside the ' Properties ' Tab. (as shown in the below figure) 2. Right Click on the Error as mentioned in the below figure. in The context menu click on the ' Quick Fix ' item as shown below in the figure. 3. Select the correct Java Project Facet from the ' Quick Fix ' Window. and click on the ' Finish ' Button. 4.  After Clicking on '
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Some Important Facts About Core Java

There are 4 important OOPS concepts in Java : Inheritance, Abstraction, Encapsulation and Polymorphism. There are two types of variables in Java : Primitive types and Object Types The default value of Boolean is false (the same applies for the Wrapper class too). Marker interface is the one which doesn't contains any methods , it is like empty interface. You cannot override the 'main' method of the Java, even-though if you try to do so it will not give any exception, program compiles and executes fine. The reason is : 'main' method is of type static . Static methods are class level methods. Even-though it looks like method overriding, it is not overriding. These are two different method with respect to the corresponding class. You can Overload the 'main' method of Java, it is valid in Java. You can have only one 'Public' class and any number of non-public classes in any java source file. Inheritance is an example for IS-A relationship. C
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