Java错误消息“无法解析为变量”？

发布时间：2020-12-15 08:45:23 所属栏目：Java 来源：网络整理

导读：好吧所以我对 java有点新意,我正在尝试创建一个类,它可以要求用户输入一个12位长的upc代码,检查以确保它是一个有效的代码,然后显示它是否是或不.我当前的程序有很多错误,我似乎无法弄明白.这是我到目前为止的代码： public class Upc { private long upc; pu

好吧所以我对 java有点新意,我正在尝试创建一个类,它可以要求用户输入一个12位长的upc代码,检查以确保它是一个有效的代码,然后显示它是否是或不.我当前的程序有很多错误,我似乎无法弄明白.这是我到目前为止的代码：

public class Upc {
    private long upc;

    public Upc(long upcs) {
        upc = upcs;
    }

    public long getUpc() {

        int m = (n2 + n4 + n6 + n8 + n10);
        long n = (n1 + n3 + n5 + n7 + n9 + n11);
        long r = (10 - (m + 3 * n) % 10);

        long n12 = (int) (upc % 10);
        upc /= 10;
        long n11 = (int) (upc % 10);
        upc /= 10;
        long n10 = (int) (upc % 10);
        upc /= 10;
        long n9 = (int) (upc % 10);
        upc /= 10;
        long n8 = (int) (upc % 10);
        upc /= 10;
        long n7 = (int) (upc % 10);
        upc /= 10;
        long n6 = (int) (upc % 10);
        upc /= 10;
        long n5 = (int) (upc % 10);
        upc /= 10;
        long n4 = (int) (upc % 10);
        upc /= 10;
        long n3 = (int) (upc % 10);
        upc /= 10;
        long n2 = (int) (upc % 10);
        upc /= 10;
        long n1 = (int) (upc % 10);

        if (r == n12) {
            return (upc + " is a feasible UPC code");
        } else {
            return (upc + " is an invalid UPC code");
        }
    }
}

我的错误如下：

13 errors found:
File: C:UsersAndrewDownloadsUpc.java  [line: 10]
Error: n2 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 10]
Error: n4 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 10]
Error: n6 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 10]
Error: n8 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 10]
Error: n10 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n1 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n3 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n5 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n7 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n9 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 11]
Error: n11 cannot be resolved to a variable
File: C:UsersAndrewDownloadsUpc.java  [line: 39]
Error: Type mismatch: cannot convert from java.lang.String to long
File: C:UsersAndrewDownloadsUpc.java  [line: 42]
Error: Type mismatch: cannot convert from java.lang.String to long

我觉得修一两件事会消除很多这个,有人能帮帮我吗？

解决方法

这个变量定义在之后

long n12 = (int) (upc%10);
upc /= 10;
long n11 = (int) (upc%10);
upc /= 10;
long n10 = (int) (upc%10);
upc /= 10;
long n9 = (int) (upc%10);
upc /= 10;
long n8 = (int) (upc%10);
upc /= 10;
long n7 = (int) (upc%10);
upc /= 10;
long n6 = (int) (upc%10);
upc /= 10;
long n5 = (int) (upc%10);
upc /= 10;
long n4 = (int) (upc%10);
upc /= 10;
long n3 = (int) (upc%10);
upc /= 10;
long n2 = (int) (upc%10);
upc /= 10;
long n1 = (int) (upc%10);



int m = (n2 + n4 + n6 + n8 + n10);
long n = (n1 + n3 + n5 + n7 + n9 + n11);
long r = (10-(m+3*n)%10);

你使用那个尚未定义的变量,并在使用后定义变量

编辑：对于if

当您使用返回值定义方法时,如果您返回String值,请参阅返回值

return (upc + " is a feasible UPC code");

你需要在方法或返回时更改返回类型,就像你想要返回它一样,那么你的方法签名就像这样

public long getUpc(){
  // and return will work
  return (upc + " is a feasible UPC code"); 
}

但是如果你只想要数值,那么不要改变它的方法签名只需像这样返回upc

return upc;

（编辑：李大同）

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