红猎人的空间

今天心血来潮写个Java swing 的程序,没想到编译通过后无法运行,显示:

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Exception in thread "main" java.lang.ExceptionInInitializerError
    at javax.swing.JPanel.updateUI(JPanel.java:109)
    at javax.swing.JPanel.(JPanel.java:69)
    at javax.swing.JPanel.(JPanel.java:92)
    at javax.swing.JPanel.(JPanel.java:100)
    at javax.swing.JRootPane.createGlassPane(JRootPane.java: