Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

98 public void actionPerformed(ActionEvent e) {
99 calculate('+');
100 }
101 });
102 jmiSub.addActionListener(new ActionListener() {
103 @Override
104 public void actionPerformed(ActionEvent e) {
105 calculate('-');
106 }
107 });
108 jmiMul.addActionListener(new ActionListener() {
109 @Override
110 public void actionPerformed(ActionEvent e) {
111 calculate('*');
112 }
113 });
114 jmiDiv.addActionListener(new ActionListener() {
115 @Override
116 public void actionPerformed(ActionEvent e) {
117 calculate('/');
118 }
119 });
120 jmiClose.addActionListener(new ActionListener() {
121 @Override
122 public void actionPerformed(ActionEvent e) {
123 System.exit(1);
124 }
125 });
126 }
127
128 /** Calculate and show the result in jtfResult */
129 private void calculate(char operator) {
130 // Obtain Number 1 and Number 2
131 int num1 = (Integer.parseInt(jtfNum1.getText().trim()));
132 int num2 = (Integer.parseInt(jtfNum2.getText().trim()));
133 int result = 0;
134
135 // Perform selected operation
136 switch (operator) {
137 case '+': result = num1 + num2;
138 break;
139 case '-': result = num1 - num2;
140 break;
141 case '*': result = num1 * num2;
142 break;
143 case '/': result = num1 / num2;
144 }
145
146 // Set result in jtfResult
147 jtfResult.setText(String.valueOf(result));
148 }
149 }
The program creates a menu bar, jmb, which holds two menus:
operationMenu and exitMenu (lines 17-30). The operationMenu
contains four menu items for doing arithmetic: Add, Subtract,
Multiply, and Divide. The exitMenu contains the menu item Close
for exiting the program. The menu items in the Operation menu are
created with keyboard mnemonics and accelerators.
The user enters two numbers in the number fields. When an
operation is chosen from the menu, its result, involving two
numbers, is displayed in the Result field. The user can also
click the buttons to perform the same operation.
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