BMI，Body Mass Index，身体质量指数，是用体重公斤数 除以 身高米数平方得出的，是目前国际上常用的衡量人体胖瘦程度以及是否健康的一个标准。
而本文通过运用Java Swing实现了一个简单的BMI计算器。
最终运行界面：
功能：可以选择三个标准：中国、亚洲、WHO，计算结果稍有不同
计算公式：BMI =weight / (height*height) 即（体重公斤数）除以（身高米数的平方）
import javax.swing.*;import javax.swing.border.EmptyBorder;import java.awt.*;import java.text.DecimalFormat;import java.util.regex.*;public class WeightIndex extends JFrame {private static final long serialVersionUID = 1L;private JPanel contentPane;private JLabel titleLabel;private JPanel contentPanel;private JButton submitButton;private ButtonGroup bg;private JPanel sexPanel;private JRadioButton ChinaRadio;private JRadioButton AsiaRadio;private JRadioButton WHORadio;private JPanel whPanel;private JLabel heightLabel;private JLabel weightLabel;private JTextField heightText;private JTextField weightText;private JPanel consolePanel;private JLabel consoleLabel;private JTextField consoleText;/*** 体重*/private double weight;/*** 身高*/private double height;/*** BMI指数*/private double BMI;/*** Launch the application.*/public static void main(String[] args) {EventQueue.invokeLater(() -> {try {WeightIndex frame = new WeightIndex();frame.pack();frame.setVisible(true);} catch (Exception e) {e.printStackTrace();}});}/*** Create the frame.*/public WeightIndex() {setTitle("身高体重指数计算器v1.0");setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);setBounds(100, 100, 450, 300);//主容器contentPane = new JPanel();contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));contentPane.setLayout(new BorderLayout(0, 0));setContentPane(contentPane);//标题，主容器北titleLabel = new JLabel("身高体重指数计算器");titleLabel.setHorizontalAlignment(SwingConstants.CENTER);contentPane.add(titleLabel, BorderLayout.NORTH);//存放选项的panel，主容器中contentPanel = new JPanel();contentPanel.setLayout(new BorderLayout());contentPane.add(contentPanel, BorderLayout.CENTER);//提交按钮，主容器南submitButton = new JButton("计算");contentPane.add(submitButton, BorderLayout.SOUTH);//存放性别选择的panel，选项北bg = new ButtonGroup();sexPanel = new JPanel();sexPanel.setLayout(new FlowLayout());contentPanel.add(sexPanel, BorderLayout.NORTH);ChinaRadio = new JRadioButton("中国标准");ChinaRadio.setSelected(true);AsiaRadio = new JRadioButton("亚洲标准");WHORadio = new JRadioButton("WHO（世界卫生组织）标准");bg.add(ChinaRadio);bg.add(AsiaRadio);bg.add(WHORadio);sexPanel.add(ChinaRadio);sexPanel.add(AsiaRadio);sexPanel.add(WHORadio);//存放身高体重的panel，选项中whPanel = new JPanel();whPanel.setLayout(new FlowLayout());contentPanel.add(whPanel, BorderLayout.CENTER);heightLabel = new JLabel("身高（米/m）：");weightLabel = new JLabel("体重（千克/kg）：");heightText = new JTextField(10);heightText.setToolTipText("请输入身高");weightText = new JTextField(10);weightText.setToolTipText("请输入体重");whPanel.add(heightLabel);whPanel.add(heightText);whPanel.add(weightLabel);whPanel.add(weightText);//结果consolePanel = new JPanel();consolePanel.setLayout(new FlowLayout());consoleLabel = new JLabel("你的身体质量指数为：");consoleText = new JTextField(28);consoleText.setEditable(false);consolePanel.add(consoleLabel);consolePanel.add(consoleText);contentPanel.add(consolePanel, BorderLayout.SOUTH);submitButton.addActionListener(e -> {String hstr = heightText.getText();String wstr = weightText.getText();Pattern pattern = pile("^[0-9]+(.[0-9]+)?$");Matcher hisNum = pattern.matcher(hstr);Matcher wisNum = pattern.matcher(wstr);boolean acc = true;if (!hisNum.matches() || !wisNum.matches()) {acc = false;}if (acc) {height = Double.parseDouble(hstr);weight = Double.parseDouble(wstr);BMI = weight / (height * height);DecimalFormat df = new DecimalFormat("#.0");String out = "";if (ChinaRadio.isSelected()) {if (BMI < 18.5) {out = "偏瘦，瘦骨嶙峋的，多吃点吧！";} else if (BMI < 23.9) {out = "正常，棒棒哒！";} else if (BMI < 28) {out = "偏胖，你胖你就运动减肥！";} else if (BMI >= 28) {out = "肥胖，现在减肥来的及！";} else {out = "外星人派来的你哦，请重新输入！";}} else if (AsiaRadio.isSelected()) {if (BMI < 18.5) {out = "偏瘦，瘦骨嶙峋的，多吃点吧！";} else if (BMI < 22.9) {out = "正常，棒棒哒！";} else if (BMI < 24.9) {out = "偏胖，你胖你就运动减肥！";} else if (BMI < 30) {out = "肥胖，现在减肥来的及！";} else if (BMI >= 30) {out = "重度肥胖，不是一般人，赶紧减肥吧！";} else {out = "外星人派来的你哦，请重新输入！";}} else {if (BMI < 18.5) {out = "偏瘦，瘦骨嶙峋的，多吃点吧！";} else if (BMI < 24.9) {out = "正常，棒棒哒！";} else if (BMI < 29.9) {out = "偏胖，你胖你就运动减肥！";} else if (BMI < 34.9) {out = "肥胖，现在减肥来的及！";} else if (BMI < 39.9) {out = "重度肥胖，不是一般人，赶紧减肥吧！";} else if (BMI >= 40) {out = "极重度肥胖,那可能得去医院看看咯！";} else {out = "外星人派来的你哦，请重新输入！";}}consoleText.setText("你的指数为：" + df.format(BMI) + "，你的健康状况为：" + out);}});}}
0419，对代码进行了部分重构。
