首先使用有效用户,效果很好第二次尝试使用新名称失败!
// First use of validUser works perfectly
username = "Fred";
password ="Flintstone";
User validUser = new User(username,password);
data.add(validUser);
System.out.println("Successful!");
// Second attempt with new names fails!
username = "John";
password = "doe";
User validUser = new User(username,password);
// ERROR: variable validUser is already defined
// I just want to put two records into the DB.
// Can't I (or how can I) just reuse validUser?
// I tried to take "new" out but that didn't work either. Thanks!
data.add(validUser);
如果要重用相同的变量,只需重新分配引用。validUser = new User(...);
在数据类型之前,就像您要在相同范围内两次声明相同变量->禁止。
通过这种方式避免这种变量的重新分配。它易于出错,并降低了代码的可读性(首选不可变变量)。只是声明新的,或者根本不需要通过在需要的地方内联它们来声明。像这样。data.add(new User());