public class StringTest {        public static void main(String[] args) {                        //判断是null还是空字符串        boolean b1 = Strings.isNullOrEmpty(null);                //判断是null还是空字符串        boolean b2 = Strings.isNullOrEmpty("");                //null转换成空        String s1 = Strings.nullToEmpty(null);                    //null转换成空        String s2 = Strings.nullToEmpty("");                //空转换成null        String s3 = Strings.emptyToNull("");        String s4 = Strings.emptyTonull(null);                System.out.println(b1);        System.out.println(b2);        System.out.println(s1);        System.out.println(s2);        System.out.println(s3);                }}//打印结果truetruenull null

注意：nullToEmpty 是转换成空格了