Java 字符串大小写转化

@Test
public void test07() {
    String str01 = "ABCDefg";
    String str02 = "abcdefg";
    System.out.println("转成小写：" + str01.toLowerCase());
    System.out.println("转成大写：" + str02.toUpperCase());

    String str03 = "abcdefg";
    String str04 = "ABCDEFG";
    System.out.println("toLowerCase() 返回原字符串：" + str03.toLowerCase());
    System.out.println("toUpperCase() 返回原字符串：" + str04.toUpperCase());

    String str05 = "Abcdefg1234中文**";
    System.out.println("转成小写：" + str05.toLowerCase());
    System.out.println("转成大写：" + str05.toUpperCase());
}