java – 将字符串拆分为两半

我正在制作一个新的转换软件来隐藏消息(为了好玩).我做了一个二进制和十进制转换类,我的想法是,用户输入字符串,它将所有转换为二进制格式.然后将它分成两半,将一半转换为十进制,然后再将字符串重新添加到一起,使其成为二进制和十进制的混合.在其他版本中,我将添加更多转换,更多分割,也可能转换为语言.我需要将字符串分成两半.到目前为止这是我的代码::

public ray() {
    Scanner in = new Scanner(System.in);

    while (true) {
        System.out.println("Please input the text you wish to encode!");
        System.out.println("Type '#' to quit the Software.");
        String s1 = in.nextLine();
        if ("#".equalsIgnoreCase(s1)) {
            System.out.println("Goodbye,hope you enjoyed RAYConversion v1.0 Alpha.");
            // close software
        }

        // convert all to binary
        binary Binary = new binary();

        //what i need to do is split stirng s1 in half,make it into different strings. Then I will convert
        //the two strings to binary and decimal. I made a converter for that.

    }
}