1 /*      EinfacherRechner.java
2  *
3  *      ein einfacher String-Berechner, der den Umgang mit
4  *      dem JAVA StringTokenizer zeigt. Beherrscht die
5  *      Addition und Subtraktion.
6  *
7  *      Details: http://www.kiesler.at/
8  *
9  */
10 
11 
12 import java.io.*;
13 import java.util.*;
14 
15 
16 public class EinfacherRechner {
17 
18 
19         public static int berechne(String s)
20                 throws Exception
21         {
22                 int result=0, zahl=0;
23                 String lastop="";
24                 boolean op=true;
25 
26                 StringTokenizer st=new
27                         StringTokenizer(s, "+-", true);
28 
29                 if((st.countTokens() % 2) != 1)
30                         throw new Exception("Anzahl der "+
31                                 "Tokens muß ungerade sein!");
32 
33                 while(st.hasMoreTokens()) {
34 
35                         if(op) {
36                                 zahl=Integer.parseInt(
37                                         st.nextToken());
38 
39                                 if(lastop.equals(""))
40                                         result=zahl;
41                                 else
42                                 if(lastop.equals("+"))
43                                         result+=zahl;
44                                 else
45                                 if(lastop.equals("-"))
46                                         result*=zahl;
47                                 else
48                                 throw new Exception
49                                         ("Unbekannte Operation '"+
50                                          lastop+"'");
51 
52                         } else
53 
54                                 lastop=st.nextToken();
55 
56                         op=!op;
57                 }
58 
59                 return(result);
60         }
61 
62 
63         public static void main(String args[])
64                 throws Exception {
65 
66                 InputStreamReader ins=new InputStreamReader(System.in);
67                 BufferedReader reader=new BufferedReader(ins);
68 
69                 try {
70 
71                         String eingabe=reader.readLine();
72                         System.out.println(berechne(eingabe));
73 
74                 } catch(Exception e) {
75 
76                         System.err.println("Problem: "+e);
77 
78                 }
79 
80         }
81 }