写一个能够随机冒出四个小写字母组成一个单词（不非得是有意义的英文单词）的程序，程序要向用户提问需要编出多少个单词出来，并且提示只能在1到500之间。

Write a Java program that will generate random four letter words. The words must consist of only lower case letters. The program will prompt the user to enter the number of words to generate.

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