ClassNotFoundException vs NoClassDefFoundError

java.lang.ClassNotFoundException

 This exception indicates that the class was not found on the classpath. This indicates that we were trying to load the class definition, and the class did not exist on the classpath.

这个异常说明你要load的class文件不在classpath

 

java.lang.NoClassDefFoundError这个error并不是说明这个class文件在classpath找不到，比如你new Class A(),而A的static块依赖了class B，B找不到，这个时候就会有NoClassDefFoundError A了，

下面一个例子也可以说明

public class NoClassDefFoundErrorDemo {
    public static void main(String[] args) {
        try {
            // The following line would throw ExceptionInInitializerError
            SimpleCalculator calculator1 = new SimpleCalculator();
        } catch (Throwable t) {
            System.out.println(t);
        }
        // The following line would cause NoClassDefFoundError
        SimpleCalculator calculator2 = new SimpleCalculator();
    }

}