问题
i have a homework assignment where i need to create a calculator that accepts the user input in this form [1+2/3*5-4]. im not supposed to use an array to store the values from the string. instead im supposed to take 3 numbers and 2 operators at a time. my question is how do i store the numbers and operators and once i store them and calculate the value get q new number and a new operator from the original string. this is what i have so far not sure if im in the right direction.
public class ExpresionEvaluation {
private static String expresion;
static double o1;
static double o2;
private static double o3;
private static char operator1;
private static char operator2;
public static double getO1(String s){
s=s.trim();
String r ="";
while (s.length()>0 && s.charAt(0)>='0' && s.charAt(0)<='9'){
r = r + s.charAt(0);
s = s.substring(1);
}
o1 = Double.parseDouble(r);
return(o1);
}
public static char getOperator1(String s){
s=s.trim();
char r;
while (s.length()>0 && s.charAt(0)>='0' && s.charAt(0)<='9'){
r = s.charAt(1);
s = s.substring(2);
}
r = operator1;
return(r);
}
public static double getO2(String s){
s=s.trim();
String r ="";
while (s.length()>0 && s.charAt(0)>='0' && s.charAt(0)<='9'){
r = r + s.charAt(2);
s = s.substring(3);
}
o2 = Double.parseDouble(r);
return(o2);
}
public static char getOperator2(String s){
s=s.trim();
char r;
while (s.length()>0 && s.charAt(0)>='0' && s.charAt(0)<='9'){
r = s.charAt(3);
s = s.substring(4);
}
r = operator2;
return(operator2);
}
public static double getO3(String s){
s=s.trim();
String r ="";
while (s.length()>0 && s.charAt(0)>='0' && s.charAt(0)<='9'){
r = r + s.charAt(4);
s = s.substring(5);
}
o3 = Double.parseDouble(r);
return(o3);
}
}
回答1:
Technically you could circumvent it by using a collection class. In the java.util package, there are many classes which emulate the behavior of an an array, but are re-sizable and offer much more functionality. These include java.util.ArrayList, java.util.LinkedList, java.util.Vector (don't use that one), and java.util.Stack. The java collections framework is very extensive, and I recommend reading the docs at
http://docs.oracle.com/javase/tutorial/collections/implementations/index.html
If you're not allowed to use collections either, the only thing i can think of is using one big string and inserting some kind of a special character or sequence in between the separate sections, then using the indexOf(char, fromIndex) and substring to iterate through the sections, something like this:
final int maxwords = 5;
String strlist = "this@should@be@an@array@";
int lastindex = 0, index = 0;
for(int n= 0; n < maxwords; n ++){
index = strlist.indexOf("@",lastindex);
String substr = strlist.substring(lastindex,index);
//process substring here
System.out.println(substr);
lastindex = index + 1;
}
This a very ugly way of doing things, but its the only thing I can think of. Hope this helps.
来源：https://stackoverflow.com/questions/13095820/how-do-you-split-up-a-string-in-java-without-arrays