I started using Ant, that ships with Eclipse. It annoys me, that I get hundreds of warnings in the lines of:
[javac] warning: java\\io\\BufferedInputStr
I solved my warning with answer from Bao. I had JDK1.6 installed before. Then installed JDK1.7 and ant was stil using JKD1.6 for compiling.
What I have changed is also set the JDK for the project: right click on project > properties > Java Build Path
If you have JDK1.6 here, try to change it to JDK1.7.