Long.parseLong(String s) 其中s必须是数字形式的字符串，才能运用该函数转化为长整型。

 1 public class ConverTo 
 2     
 3     { public static void main(String [] args)
 4        { String numberIn =args[0];
 5          convertNum(numberIn);
 6         }
 7         static void convertNum(String num)
 8            {
 9               long showNumber;
10               String temp;
11                 switch(num)
12                { case "one":
13                   temp = "1";
14                   showNumber = Long.parseLong(temp);
15                   System.out.println(num+"convert to"+showNumber);
16                   break;
17                  case "two":
18                   temp = "2";
19                   showNumber = Long.parseLong(temp);
20                   System.out.println(num+"convert to"+showNumber);
21                   break;
22                  case "three":
23                   temp ="3";
24                   showNumber = Long.parseLong(temp);
25                   System.out.println(num+"convert to"+showNumber);
26                   break;
27                  case "four":
28                   temp = "4";
29                   showNumber = Long.parseLong(temp);
30                   System.out.println(num+"convert to"+showNumber);
31                   break;
32                  case "five":
33                   temp = "5";
34                   showNumber = Long.parseLong(temp);
35                   System.out.println(num+"convert to"+showNumber);
36                   break;
37                  case "six":
38                   temp = "6";
39                   showNumber = Long.parseLong(temp);
40                   System.out.println(num+"convert to"+showNumber);
41                   break;
42                  case "seven":
43                    temp = "7";
44                   showNumber = Long.parseLong(temp);
45                   System.out.println(num+"convert to"+showNumber);
46                   break;
47                  case "eight":
48                    temp = "8";
49                   showNumber = Long.parseLong(temp);
50                   System.out.println(num+"convert to"+showNumber);
51                   break;
52                  case "nine":
53                    temp = "9";
54                   showNumber = Long.parseLong(temp);
55                   System.out.println(num+"convert to"+showNumber);
56                   break;
57                  case "ten":
58                    temp = "10";
59                   showNumber = Long.parseLong(temp);
60                   System.out.println(num+"convert to"+showNumber);
61                   break;
62 
63                  }
64 
65             }
66 
67      }

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原文地址：https://www.cnblogs.com/lubocsu/p/4904692.html