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CalculatePostfixSolve.java
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CalculatePostfixSolve.java
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import java.util.Stack;
public class CalculatePostfixSolve implements Requirement2_OutputGetter
{
private String inputString;
private double resultOfExpression;
public CalculatePostfixSolve(){
this.inputString = "";
this.resultOfExpression = 0;
}
public CalculatePostfixSolve(String inputString){
this.inputString = inputString;
this.resultOfExpression = 0;
}
public void setInputString(String inputString){
this.inputString = inputString;
}
public double getResultOfExpression(){
this.resultOfExpression = calculatePostfix();
return this.resultOfExpression;
}
private double calculatePostfix()
{
Stack <Double> stack = new Stack <Double> ();
Double ans,n = 0.0;
String [] tokens = stringTokenizer(this.inputString);
for (int i=0; i<tokens.length; i++)
{
//Check num
if (isNum(tokens[i]))
{
stack.push(Double.parseDouble(tokens[i]));
}
else
{
n = stack.pop();
// Exponent
if (tokens[i].equals("^"))
{
ans = Math.pow(stack.pop(),n);
stack.push(ans);
}
// Multiplication
if (tokens[i].equals("*"))
{
ans = stack.pop() * n;
stack.push(ans);
}
// Division
if (tokens[i].equals("/"))
{
if (n==0 && stack.peek()==0)
{
return 0;
}
ans = stack.pop() / n;
stack.push(ans);
}
// Addition
if (tokens[i].equals("+"))
{
ans = stack.pop() + n;
stack.push(ans);
}
// Subtraction
if (tokens[i].equals("-"))
{
ans = stack.pop() - n;
stack.push(ans);
}
}
}
return stack.pop();
}
private String [] stringTokenizer(String str)
{
String [] tokens = str.split(" ");
return tokens;
}
private boolean isNum(String c)
{
return c.matches("-?\\d+(\\.\\d+)?");
}
}