Dependancy Injection (Spring Note 1)

Just assume a situation where we have to develop a module that must generate different types of reports such as PDF reports, Excel reports. One of a worst design for such scenario is design classes for each report separately without any form of polymorphism. Such a design may may result in increasing coupling of the program.
example :

ExcelReport excelReport=new ExcelReport();
PDFReport pdfReport=new PDFReport();

excelReport.initialize();
excelReport.createReport();
excelReport.saveReport();

pdfReport.initialize();
pdfReport.createReport();
pdfReport.saveReport();