thanks. your advice is very valuable. But I just need a few filter lines in java. it's all.

I'm not sure I understood exactly what you were looking for, but BX a command-line tool can create Electrum seeds. https://github.com/libbitcoin/libbitcoin-explorer/wiki/bx-electrum-new
So you can maybe call it from your Java program and take what it can return.
Otherwise you can use its C++ libraries, but afaik it's not easy at all in Java (with JNI).
At least you can maybe try to convert/adapt the C++ code in Java, https://github.com/libbitcoin/libbitcoin-system/blob/master/src/wallet/mnemonics/electrum.cpp