Java 中的計算器用於計算加法、減法、乘法、除法、模數、數字冪等。我們可以使用普通的 Java switch case 和 Java swing 獨立應用程式來執行此計算器操作。在Plain Java計算器操作中，我們不需要任何額外的函式庫，但在swing應用程式的情況下，我們必須需要java.awt.event.*，javax.swing.*，java.awt.*packages。
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JAVA 掌握 - 專業化 | 78 課程系列 | 15 次模擬測驗
方法
計算機的擺動方法：
-
add(Component 元件): 用於將元件加入容器中。
-
setSize(int x, int y): 用於根據給定尺寸設定容器的大小。
-
setText(String string): 用來設定字串文字。
-
getText():用來取得容器的文字。
-
addActionListenerListener(ActionListener actionListener): 用於給容器設定action。
-
setBackground(Color color) : 用來設定背景顏色。
如何用 Java 建立計算器？
我們可以透過兩種方式建立計算器：
- 使用 Switch Case 語句。
- 使用 Swing 圖形。
1.使用 Switch Case 語句
第1步：使用者輸入要執行操作的字符，如「+」、「-」、「*」、「/」、「%」、「^」等等
第 2 步：在 switch case 中，我們為每個角色實現了邏輯。
第 3 步：基於執行的字元運算，如加法、減法、乘法、除法、模數（求餘數）和數字的冪。
文法：
public class CalculatorSwitchCase
{
//Ask input from user
switch(character)
{
case '+'://addition operation
case '-'://subtraction operation
case '*'://multiplication operation
case '/'://division operation
case '%'://modulus operation
case '^'://power operation
}
//display output
}登入後複製
範例 #1 – Switch Case 計算器功能
代碼：
package com.calculator;
import java.util.Scanner;
public class CalculatorSwitchCase {
public static void main(String[] args) {
// declaring varibales
double firstNumber, secondNumber;
double result_operation_output;
// Creating scanner for object for allow input
Scanner scannerObject = new Scanner(System.in);
do {
System.out.println("==============================================");
System.out.println("1. + for ADDITION");
System.out.println("2. - for SUBTRACTION");
System.out.println("3. * for MULTIPLICATION");
System.out.println("5. 4. / for DIVISION");
System.out.println("6. % for REMAINDER");
System.out.println("7. ^ for POWER");
System.out.println("8. Q for QUIT");
System.out.println("==============================================");
// ask the user to enter first number
System.out.print("Enter your first number:\n");
firstNumber = scannerObject.nextDouble();
// ask the user to enter second number
System.out.print("Enter your second number:\n");
secondNumber = scannerObject.nextDouble();
System.out.print("Enter an operators like (+, -, *, /, %, ^) only:\n ");
// storing the operator in char object
char operator = scannerObject.next().charAt(0);
switch (operator) {
case '+':
result_operation_output = firstNumber + secondNumber;
break;
case '-':
result_operation_output = firstNumber - secondNumber;
break;
case '*':
result_operation_output = firstNumber * secondNumber;
break;
case '/':
result_operation_output = firstNumber / secondNumber;
break;
case '%':
result_operation_output = firstNumber % secondNumber;
break;
case '^':
result_operation_output = Math.pow(firstNumber, secondNumber);
break;
case 'Q':
System.exit(0);
default:
System.out.printf("Please enter specified operator only");
return;
}
System.out.println(firstNumber + " " + operator + " " + secondNumber + " is : " + result_operation_output);
} while (result_operation_output != 'Q');
scannerObject.close();
}
}登入後複製
輸出：
o/p 用於加法和減法
乘法和除法的o/p
餘數和冪的o/p
2.使用 Swing 圖形
Step1：建立一個類別並從 JFrame、ActionerListener 擴展它。
第 2 步：建立 0-9 的數字按鈕和 +、-、*、*、% 等字元按鈕
第三步：為所有按鈕寫一個 Action 監聽器。
第四步：將所有這些組件加入螢幕。
範例 2 – 擺動計算器
代碼：
package com.calculator.swing;
//Java program to create a simple calculator
//with basic +, -, /, * using java swing elements
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
@SuppressWarnings("serial")
public class CalculatorSwing extends JFrame implements ActionListener {
// create a frame
static JFrame frameToDisplay;
// create a textfield
static JTextField labeTextField;
// it store the operands and operators
String string0, string1, string2;
// constructor
CalculatorSwing() {
string0 = string1 = string2 = "";
}
// main function to java application
public static void main(String args[]) {
// create the frame to display the screen
frameToDisplay = new JFrame("My Calculator");
try {
// used to set the look and feel for the application
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception exception) {
System.err.println(exception.getMessage());
}
// create the class object
CalculatorSwing calculatorSwing = new CalculatorSwing();
// create text field
labeTextField = new JTextField(16);
// set to the non editable
labeTextField.setEditable(false);
// declaring numbers buttons and operators buttons
JButton button_0, button_1, button_2, button_3, button_4, button_5, button_6, button_7, button_8, button_9,
button_add, button_subtract, button_div, button_mul, button_dot, button_equal1, button_equal2;
// creating numbers buttons
button_0 = new JButton("0");
button_1 = new JButton("1");
button_2 = new JButton("2");
button_3 = new JButton("3");
button_4 = new JButton("4");
button_5 = new JButton("5");
button_6 = new JButton("6");
button_7 = new JButton("7");
button_8 = new JButton("8");
button_9 = new JButton("9");
// creating equals buttons
button_equal2 = new JButton("=");
// creating operators like +,-,*,/ buttons
button_add = new JButton("+");
button_subtract = new JButton("-");
button_div = new JButton("/");
button_mul = new JButton("*");
button_equal1 = new JButton("C");
// creating dot(.) buttons
button_dot = new JButton(".");
// creating panel
JPanel jPanel = new JPanel();
// adding action listeners to the buttons
button_mul.addActionListener(calculatorSwing);
button_div.addActionListener(calculatorSwing);
button_subtract.addActionListener(calculatorSwing);
button_add.addActionListener(calculatorSwing);
button_9.addActionListener(calculatorSwing);
button_8.addActionListener(calculatorSwing);
button_7.addActionListener(calculatorSwing);
button_6.addActionListener(calculatorSwing);
button_5.addActionListener(calculatorSwing);
button_4.addActionListener(calculatorSwing);
button_3.addActionListener(calculatorSwing);
button_2.addActionListener(calculatorSwing);
button_1.addActionListener(calculatorSwing);
button_0.addActionListener(calculatorSwing);
button_dot.addActionListener(calculatorSwing);
button_equal1.addActionListener(calculatorSwing);
button_equal2.addActionListener(calculatorSwing);
// add all elements to the panel
jPanel.add(labeTextField);
jPanel.add(button_add);
jPanel.add(button_1);
jPanel.add(button_2);
jPanel.add(button_3);
jPanel.add(button_subtract);
jPanel.add(button_4);
jPanel.add(button_5);
jPanel.add(button_6);
jPanel.add(button_mul);
jPanel.add(button_7);
jPanel.add(button_8);
jPanel.add(button_9);
jPanel.add(button_div);
jPanel.add(button_dot);
jPanel.add(button_0);
jPanel.add(button_equal1);
jPanel.add(button_equal2);
// set background of the panel
jPanel.setBackground(Color.darkGray);
// add the panel to the frame
frameToDisplay.add(jPanel);
frameToDisplay.setSize(210, 230);
frameToDisplay.show();
}
//action listener implementation
public void actionPerformed(ActionEvent e) {
String input = e.getActionCommand();
// check if the given value is number
if ((input.charAt(0) >= '0' && input.charAt(0) <= '9') || input.charAt(0) == '.') {
// if operand is present then add to second no
if (!string1.equals(""))
string2 = string2 + input;
else
string0 = string0 + input;
// set the value to the text
labeTextField.setText(string0 + string1 + string2);
} else if (input.charAt(0) == 'C') {
// clearing
string0 = string1 = string2 = "";
// set the value of the text
labeTextField.setText(string0 + string1 + string2);
} else if (input.charAt(0) == '=') {
double equalsInput;
// store the value in the first index
if (string1.equals("+"))
equalsInput = (Double.parseDouble(string0) + Double.parseDouble(string2));
else if (string1.equals("-"))
equalsInput = (Double.parseDouble(string0) - Double.parseDouble(string2));
else if (string1.equals("/"))
equalsInput = (Double.parseDouble(string0) / Double.parseDouble(string2));
else
equalsInput = (Double.parseDouble(string0) * Double.parseDouble(string2));
// set the value of the text
labeTextField.setText(string0 + string1 + string2 + "=" + equalsInput);
// converting int to string
string0 = Double.toString(equalsInput);
string1 = string2 = "";
} else {
// if no operand is there
if (string1.equals("") || string2.equals(""))
string1 = input;
else {
double te;
// store the value in the first index
if (string1.equals("+"))
te = (Double.parseDouble(string0) + Double.parseDouble(string2));
else if (string1.equals("-"))
te = (Double.parseDouble(string0) - Double.parseDouble(string2));
else if (string1.equals("/"))
te = (Double.parseDouble(string0) / Double.parseDouble(string2));
else
te = (Double.parseDouble(string0) * Double.parseDouble(string2));
// converting int to string
string0 = Double.toString(te);
// put the operator
string1 = input;
// take the operand as blank
string2 = "";
}
// set the value of the text
labeTextField.setText(string0 + string1 + string2);
}
}
}
登入後複製
輸出：
結論
Java計算器用於計算加、減、除、乘、模和冪等運算。這可以透過使用 switch case 語句和使用 swing API 兩種方式來完成。
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