Java小白,eclipse中导入图形界面包就会出错,程序没有问题,请大神指点。

Description Resource Path Location Type
Access restriction: The type JOptionPane is not accessible due to restriction on required library C:\Program Files\Java\jre1.8.0_20\lib\rt.jar dialog.java /myjava3/src line 4 Java Problem

环境变量 :
java_home=C:\Program Files\Java\jdk1.8.0_20 classpath=%JAVA_HOME%\lib\tools.jar;%JAVA_HOME%\lib\dt.jar;
path=%JAVA_HOME%\bin;

安装windowBuilder插件