Numerical expressions in Java are meant to mirror those of everyday algebra. The

Question

Numerical expressions in Java are meant to mirror those of everyday algebra. Therefore, arithmetic operators conform to a precedence relation; multiplication or division before addition or subtraction. Write a program called Calculator.java that implements a very simple calculator. It will accept as input exactly 3 numbers separated by two operators with no parenthesis. The allowed operators are + - * /. Output the value of the expression adhering to proper operator precedence rules. INPUT: a single line including 3 double values separated by two operators. The operators are separated from the numbers by a space. e.g. 3.4 + 2.5 * 5.7 OUTPUT: The result of the calculation as a double, printed to two decimal places The answer is supposed to look like this: Calculator.java: Input 3 decimal numbers separated by 2 operators: 10.7 + 12.4 / 6.2 The result is: 12.70 Input 3 decimal numbers separated by 2 operators: 3.23 * 5.01 + 2.44 The result is: 18.62 Input 3 decimal numbers separated by 2 operators: 8 - 4 - 4 The result is: 0.00

Explanation / Answer

import java.awt.*; import javax.swing.*; import java.awt.event.*; class Calculator implements ActionListener { int c,n; String s1,s2,s3,s4,s5; Frame f; JButton b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16; Panel p; TextField tf1; GridLayout gl; Calculator() { f=new Frame("Calculator"); p=new Panel(); b1=new JButton("0"); b1.addActionListener(this); b2=new JButton("1"); b2.addActionListener(this); b3=new JButton("2"); b3.addActionListener(this); b4=new JButton("3"); b4.addActionListener(this); b5=new JButton("4"); b5.addActionListener(this); b6=new JButton("5"); b6.addActionListener(this); b7=new JButton("6"); b7.addActionListener(this); b8=new JButton("7"); b8.addActionListener(this); b9=new JButton("8"); b9.addActionListener(this); b10=new JButton("9"); b10.addActionListener(this); b11=new JButton("+"); b11.addActionListener(this); b12=new JButton("-"); b12.addActionListener(this); b13=new JButton("x"); b13.addActionListener(this); b14=new JButton("/"); b14.addActionListener(this); b15=new JButton("="); b15.addActionListener(this); b16=new JButton("A/C"); b16.addActionListener(this); tf1=new TextField(20); p.add(tf1); tf1.setBackground(Color.yellow); gl=new GridLayout(4,4,10,20); p.setLayout(gl); p.add(b1);p.add(b2);p.add(b3);p.add(b4);p.add(b5);p.add(b6);p.add(b7);p.add(b8);p.add(b9);p.add(b10);p.add(b11);p.add(b12);p.add(b13);p.add(b14);p.add(b15);p.add(b16); f.add(p); f.setSize(100,200); f.setVisible(true); } public void actionPerformed(ActionEvent e) { if(e.getSource()==b1) { s3=tf1.getText(); s4="0"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b2) { s3=tf1.getText(); s4="1"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b3) { s3=tf1.getText(); s4="2"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b4) { s3=tf1.getText(); s4="3"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b5) { s3=tf1.getText(); s4="4"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b6) { s3=tf1.getText(); s4="5"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b7) { s3=tf1.getText(); s4="6"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b8) { s3=tf1.getText(); s4="7"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b9) { s3=tf1.getText(); s4="8"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b10) { s3=tf1.getText(); s4="9"; s5=s3+s4; tf1.setText(s5); } if(e.getSource()==b11) { s1=tf1.getText(); tf1.setText(""); c=1; } if(e.getSource()==b12) { s1=tf1.getText(); tf1.setText(""); c=2; } if(e.getSource()==b13) { s1=tf1.getText(); tf1.setText(""); c=3; } if(e.getSource()==b14) { s1=tf1.getText(); tf1.setText(""); c=4; } if(e.getSource()==b15) { s2=tf1.getText(); if(c==1) { n=Integer.parseInt(s1)+Integer.parseInt(s2); tf1.setText(String.valueOf(n)); } else if(c==2) { n=Integer.parseInt(s1)-Integer.parseInt(s2); tf1.setText(String.valueOf(n)); } else if(c==3) { n=Integer.parseInt(s1)*Integer.parseInt(s2); tf1.setText(String.valueOf(n)); } else if(c==4) { n=Integer.parseInt(s1)/Integer.parseInt(s2); tf1.setText(String.valueOf(n)); } } if(e.getSource()==b16) { tf1.setText(""); } } public static void main(String args[]) { Calculator c=new Calculator(); } }

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