1. Open project properties.
2. Select Java Build Path node.
3. Select Libraries tab.
4. Remove JRE System Library.
5. Add Library JRE System Library. （将原来的JRE system library 移除，点击 add library，重新载入JRE
system library ）
经验证，真的好使！！
1. Open project properties.
2. Select Java Build Path node.
3. Select Libraries tab.
4. Remove JRE System Library.
5. Add Library JRE System Library. （将原来的JRE system library 移除，点击 add library，重新载入JRE
system library ）
经验证，真的好使！！