Cannot invoke "com.example.demo1.entity.Users.getName()" because "users" is null

This error means that you are trying to call the `getName()` method on a null object reference. In other words, the `users` object has not been initialized properly, or it has been set to null somewhere in your code.

To fix this error, you need to make sure that the `users` object is properly initialized before calling any of its methods. This could involve checking for null values before calling methods, or initializing the object with default values if it is null.

It's also possible that the error is caused by a typo or other mistake in your code. Make sure that you are referencing the correct object, and that you are calling the correct method on that object.

相关问题

验证码 Cannot invoke "String.toLowerCase()" because the return value of "com.example.demo.entity.User.getVarCode()" is null

验证码错误提示 "Cannot invoke "String.toLowerCase()" because the return value of "com.example.demo.entity.User.getVarCode()" is null"，意味着在尝试调用 `User` 对象的 `getVarCode()` 方法获取验证码字符串之后，该方法返回了 `null`。在对 `null` 调用 `toLowerCase()` 这种需要非空值的方法时，会抛出 `NullPointerException`。

这种情况通常出现在用户未输入验证码、验证码已被清除或者从数据库查询出来的验证码数据有误的情况下。为了修复这个问题，你需要先检查 `getVarCode()` 返回的是否为空，再进行后续的操作，例如：

User user = ...; // 获取 User 实例
String varCode = user.getVarCode();
if (varCode != null) {
    String lowerCaseCode = varCode.toLowerCase(); // 转换为小写
    // 其他验证操作...
} else {
    throw new NullPointerException("验证码不能为空");
}