java - How do I create a memory for a calculator with hashmap? -
okay building simple postfix calculator in java , asked create couple functions it, 1 struggling memory. heard hashmap, , did research on it, don't think quite understand how implement program yet. way program work user start , postfix calculator , prompted input this:
java postfixcalc integer postfix calculator memory > but has option assign variable input, example:
> = 3 5 + 1 - 7 > bee = 3 * 21 > bee + 28 > bee 3 % 0 > = 4 4 > 57 57 > 2 c + c not found > mem a: 4 bee: 21 > exit here's code far. im figuring should tokenize input , put in array list first in order variable name, unless theres better way.
import java.util.*; import java.io.*; public class program6 { public static void main(string args[]) { system.out.println("servando hernandez"); system.out.println("rpn command line calculator"); scanner scan = new scanner(system.in); system.out.print(">"); while(scan.hasnextline()) { system.out.print("> "); string = scan.nextline(); string b = "quit"; string c = "mem"; string d = "clear"; if(a.equals(b)) { system.exit(0); } else { system.out.println(compute(a)); } system.out.print(">"); } } public static string compute(string input) { list<string> processedlist = new arraylist<string>(); if (!input.isempty()) { stringtokenizer st = new stringtokenizer(input); while (st.hasmoretokens()) { processedlist.add(st.nexttoken()); } } else { return "error"; } stack<string> templist = new stack<string>(); iterator<string> iter = processedlist.iterator(); while (iter.hasnext()) { string temp = iter.next(); if (temp.matches("[0-9]*")) { templist.push(temp); } else if (temp.matches("[*-/+]")) { if (temp.equals("*")) { int rs = integer.parseint(templist.pop()); int ls = integer.parseint(templist.pop()); int result = ls * rs; templist.push("" + result); } else if (temp.equals("-")) { int rs = integer.parseint(templist.pop()); int ls = integer.parseint(templist.pop()); int result = ls - rs; templist.push("" + result); } else if (temp.equals("/")) { int rs = integer.parseint(templist.pop()); int ls = integer.parseint(templist.pop()); int result = ls / rs; templist.push("" + result); } else if (temp.equals("+")) { int rs = integer.parseint(templist.pop()); int ls = integer.parseint(templist.pop()); int result = ls + rs; templist.push("" + result); } } else { return "error"; } } return templist.pop(); } } private static string hashmap(string q) { list<string> memory = new arraylist<string>(); if(!q.isempty()) { stringtokenizer var = new stringtokenizer(q); while(q.hasmoretokens()) { memory.add(q.nexttoken()); } } hashmap h = new hashmap(); } }//end of class
i think idea of hash map memory insert key-value pairs key variable name (a string) , value value of variable (an integer).
e.g., after evaluating a = 3 5 + 1 - add ("a", 7) memory hash map. when want evaluate bee = 3 * can value of a in hashmap, 7, , calculation that. after calculation add ("bee", 21) memory hash map.
and on that.
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