on building ros_core i run command: ./gradlew install

i got error:

Downloading http://services.gradle.org/distributions/gradle-1.0-milestone-9-bin.zip

Exception in thread "main" java.net.UnknownHostException: services.gradle.org at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:175) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:384) at java.net.Socket.connect(Socket.java:546) at java.net.Socket.connect(Socket.java:495) at sun.net.NetworkClient.doConnect(NetworkClient.java:178) at sun.net.www.http.HttpClient.openServer(HttpClient.java:409) at sun.net.www.http.HttpClient.openServer(HttpClient.java:530) at sun.net.www.http.HttpClient.(HttpClient.java:240) at sun.net.www.http.HttpClient.New(HttpClient.java:321) at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:942) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:890) at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:801) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1139) at org.gradle.wrapper.Download.downloadInternal(Download.java:61) at org.gradle.wrapper.Download.download(Download.java:49) at org.gradle.wrapper.Install.createDist(Install.java:51) at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:129) at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:47) kushagra@kushagra:~/rosworkspace/rosjavacore$ ./gradlew install Downloading http://services.gradle.org/distributions/gradle-1.0-milestone-9-bin.zip

Exception in thread "main" java.net.UnknownHostException: services.gradle.org at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:175) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:384) at java.net.Socket.connect(Socket.java:546) at java.net.Socket.connect(Socket.java:495) at sun.net.NetworkClient.doConnect(NetworkClient.java:178) at sun.net.www.http.HttpClient.openServer(HttpClient.java:409) at sun.net.www.http.HttpClient.openServer(HttpClient.java:530) at sun.net.www.http.HttpClient.(HttpClient.java:240) at sun.net.www.http.HttpClient.New(HttpClient.java:321) at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:942) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:890) at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:801) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1139) at org.gradle.wrapper.Download.downloadInternal(Download.java:61) at org.gradle.wrapper.Download.download(Download.java:49) at org.gradle.wrapper.Install.createDist(Install.java:51) at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:129) at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:47)

PLEASE HELP :(