Question

JAVA

Stack - Implementation.

You will be able to use the push, pop and peek of Stack concept. Post-Fix calculator - When an arithmetic expression is presented in the postfix form, you can use a stack to evaluate the expression to get the final value. For example: the expression 3 + 5 * 9 (which is in the usual infix form) can be written as 3 5 9 * + in the postfix. More interestingly, post form removes all parentheses and thus all implicit precedence rules.

Program Implementation Requirements

Use the stack concept to create a post-fix calculator. I will be using a test-harnessPreview the document to run your program. Please make sure it meets the requirements to be run by the test harness.

Test harness:

public class StackCalcTest {

public static void main(String[] args) {

StackCalc stackCalc = new StackCalc();

String[] values = {"3", "5", "9", "*", "+"};

for(int i = 0; i < 5; i++) {

stackCalc.stack.push(values[i]);

}

System.out.println(stackCalc.stack);

System.out.println(stackCalc.answer()); }}

Answer 1

import java.util.Stack;

public class StackCalc{

Stack<String> stack = null;

StackCalc(){

stack = new Stack<String>();

}

public double answer() {

Stack<String> temp = new Stack<String>();

String s = "";

while(!stack.isEmpty()) {

String k = stack.peek();

s = s + k;

temp.push(k);

stack.pop();

}

Stack<Double> postfix = new Stack<Double>();

for (int i = s.length()-1; i>=0; i--) {

char c = s.charAt(i);

if (Character.isDigit(c))

postfix.push((double) (c - '0'));

else {

double val1 = postfix.peek();

postfix.pop();

double val2 = postfix.peek();

postfix.pop();

switch (c) {

case '+':

postfix.push(val2 + val1);

break;

case '-':

postfix.push(val2 - val1);

break;

case '/':

postfix.push(val2 / val1);

break;

case '*':

postfix.push(val2 * val1);

break;

}

}

}

return postfix.peek();

}

}

****************************************************************************

public class StackCalcTest {

public static void main(String[] args) {

StackCalc stackCalc = new StackCalc();

String[] values = { "3", "5", "9", "*", "+" };

for (int i = 0; i < 5; i++) {

stackCalc.stack.push(values[i]);

}

System.out.println(stackCalc.stack);

System.out.println(stackCalc.answer());

}

}

***************************************************************************

SEE OUTPUT

Thanks, PLEASE COMMENT if there is any concern.