java如何拆分一个带有字符数且字符为空白的字符串

Question

我想把一个字符串拆分成每行最大字符数的行，而只拆分空白

例如：

如果我的字符串是good morning , today is monday good morning , today is monday 字符数：11

输出应该是

good
morning , 
today is 
monday good
morning , 
today is 
monday

这是我的两行代码

public String skipRowLettreNumbre(String lettre) {
        String ret = lettre + "\n";
        if (lettre.length() > 36) {
        String after50 = lettre.substring(36);
        for (int i = 0; i < after50.length(); i++) {
            if (after50.substring(i, i + 1).equals(" ")) {
                String part1 = lettre.substring(0, i + 36);
                String part2 = lettre.substring(i + 36, lettre.length());
                ret = part1 + "\n   " + part2;
                break;
            }
        }
    }
    return ret + "";
}