Jasper Report + iReport + NetBeans 4

[chinomoreno]

Alguien me puede ayudar estoy tratando de multiplicar dos campos pero me marca errores

Errors compiling .\Reporte_departemaneto.jasper.
net.sf.jasperreports.engine.JRException:*Errors*we re*encountered*when*compiling*report*expressions*c lass*file: 1.*Cannot*cast*from*Double*to*String ****************value*=*(java.lang.String)(new*jav a.lang.Double(**(((java.lang.Double)field_opportun ities_amount.getValue()).doubleValue())**(((java.l ang.Double)field_opportunities_probability.getValu e()).doubleValue())*));//$JR_EXPR_ID=10$ ************************<----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------> 2.*Cannot*cast*from*Double*to*String ****************value*=*(java.lang.String)(new*jav a.lang.Double(**(((java.lang.Double)field_opportun ities_amount.getOldValue()).doubleValue())**(((jav a.lang.Double)field_opportunities_probability.getO ldValue()).doubleValue())*));//$JR_EXPR_ID=10$ ************************<----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------> 3.*Cannot*cast*from*Double*to*String ****************value*=*(java.lang.String)(new*jav a.lang.Double(**(((java.lang.Double)field_opportun ities_amount.getValue()).doubleValue())**(((java.l ang.Double)field_opportunities_probability.getValu e()).doubleValue())*));//$JR_EXPR_ID=10$ ************************<----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------> 3*errors ****at*net.sf.jasperreports.engine.design.JRAbstra ctCompiler.compileReport(JRAbstractCompiler.java:1 93) ****at*it.businesslogic.ireport.IReportCompiler.ru n(IReportCompiler.java:591) ****at*java.lang.Thread.run(Unknown*Source)