Exchage Web服務

我現在用的是Exhange Web服務的Java插件在NetBeans在Java 7中，Exchage Web服務

代碼

ExchangeService service = new 
      ExchangeService(ExchangeVersion.Exchange2007_SP1); 

    ExchangeCredentials credentials = new WebCredentials 
      ("domain\\user","pass"); 
    service.setCredentials(credentials); 
    service.autodiscoverUrl("email");

我面對這個錯誤

java.lang.UnsupportedClassVersionError: microsoft/exchange/webservices/data/ExchangeCredentials : Unsupported major.minor version 51.0 
at java.lang.ClassLoader.defineClass1(Native Method) 
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) 
at java.lang.ClassLoader.defineClass(ClassLoader.java:615) 
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) 
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) 
at java.net.URLClassLoader.access$000(URLClassLoader.java:58) 
at java.net.URLClassLoader$1.run(URLClassLoader.java:197) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.net.URLClassLoader.findClass(URLClassLoader.java:190) 
at java.lang.ClassLoader.loadClass(ClassLoader.java:306) 
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) 
at java.lang.ClassLoader.loadClass(ClassLoader.java:247) 
Could not find the main class: TestMail.ews.TestJavaMail. Program will exit. 
Exception in thread "main" Java Result: 1

我試圖改變設置項目 - >屬性 - >源選項卡 - >源/二進制組合框到JDK 5.仍然給我錯誤