Your code relies on a contract defined by the interface rather than a concrete implementation. When createSheet() switches over to another implementation that implements WritableSheet then you do not have to change anything in your client code! One major advantage is that the implementation used internally by createSheet() can be changed silently without affecting client code that uses it.
But we can cast an object of any class implementing the interface to the type WritableSheet. Be sure to comprehend that we did not create an object of WritableSheet - we cannot since it is an interface. Since createSheet()'s return type is WritableSheet it is casted to the type WritableSheet. It is internally using a concrete class that is implementing WritableSheet and returning an object of it. The static factory method createSheet() is doing sth like that. It can be casted to the contract - we say you can cast any object from a class implementing an interface to this interface type. You can see any object created by a class that signed a contract as an object of this contract. Interfaces in Java are defining a contract and they're types! There may be several classes signing this contract - we say these classes are implementing the interface. Java Excel API) is the most widely used API for executing Selenium data-driven tests, which allows users to read, write, create, and modify sheets in an Excel(.xls) workbook at runtime. Please would you clarify me that? At the end the code works, but it's not clear how those interfaces (Sheet and WritableSheet) are working. Although Log4j 2 is broken up between an API and an implementation, the primary purpose of doing so was not to allow multiple implementations, although. While sheet was the previous implementation of what? Of an interface seems to me.Īnd which method they are using, if interfaces provide abstract method? The Log4j 2 API provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation. No problem the first line, I create a new element, a label (that is a text cell) īut the second? again, addCell is a interface method seeing the api! Then in the sample code I arrive to this: Label lblNome = new Label(0, 1, "Nome:") While, then, using the createSheet method (provided by WritableWorkbook), it seems I'm creating a WritableSheet. But, I thought that I wasn't able to create an object from an interface. And "WritableSheet" is a subinterface of another interface, which is "Sheet". The sheet is a "WritableSheet", but this is an interface! And seeing the api, there are no implementing classes. And until this, I'm there.īut, then, what am I doing in the second instruction? I'm creating the workbook using the static method provided by Workbook that is a superclass of WritableWorkbook. That is, the workbook object was previously instantiated and is a WritableWorkbook object. WritableSheet sheet = workbook.createSheet("first sheet", 0) So I was studying a sample code of jxl api, to write and read an excel file, and I arrived to this point: workbook = Workbook.createWorkbook(new File("/home/me/workspace/files/output.xls")) Well I know that an interface 'provides' only abstract methods to be implemented by the concrete subclasses. WorkSheet.addCell(new 'm quite new to Java and am stuck with this, please. tVerticalAlignment(VerticalAlignment.CENTRE) WritableCellFormat normalFormat = new WritableCellFormat(normalFont) creating plain format to write data in excel sheet WritableFont normalFont = new WritableFont(WritableFont.createFont("MS Sans Serif"), Creating Writable font to be used in the report SheetSettings sh = workSheet.getSettings() WorkSheet = workbook.createSheet("Test Report" ,0) WritableWorkbook workbook = Workbook.createWorkbook(new File("E:/Tips/JExcelTip/TestReport.xls"), ws) WorkbookSettings ws = new WorkbookSettings() It supports different formatting of cells and fonts as well as colouring and shading of cells.īelow is an example code which creates a spread sheet using JExcel API. The Java Excel API allow us to dynamically create reports in excel. Sometimes we need to generate reports in excel sheet from our application.
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