From ebf699ab0ae60c5aec254f23dc0fd13a4065f442 Mon Sep 17 00:00:00 2001 From: LENOVO Date: Fri, 10 Jun 2022 00:20:42 +0800 Subject: [PATCH 1/3] =?UTF-8?q?=E6=88=91=E6=98=AF=E4=BF=A1=E7=AE=A14?= =?UTF-8?q?=E7=8F=AD30=E5=8F=B7=E5=91=A8=E5=BF=97=E5=98=89=EF=BC=8C?= =?UTF-8?q?=E9=A1=B9=E7=9B=AE=E9=83=A8=E5=88=86=E5=AE=8C=E6=88=90=E8=BF=98?= =?UTF-8?q?=E9=9C=80=E8=A1=A5=E5=85=85=EF=BC=8C=E8=AF=B7=E8=80=81=E5=B8=88?= =?UTF-8?q?=E6=A3=80=E6=9F=A5=E8=AF=84=E9=98=85=E3=80=82?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- src/java2022spring/Calculator.java | 467 +++++++++++++++++++++++++++++ 1 file changed, 467 insertions(+) create mode 100644 src/java2022spring/Calculator.java diff --git a/src/java2022spring/Calculator.java b/src/java2022spring/Calculator.java new file mode 100644 index 0000000..dba455c --- /dev/null +++ b/src/java2022spring/Calculator.java @@ -0,0 +1,467 @@ +package java2022spring; +import java.awt.*; +import java.awt.event.*; +import java.lang.reflect.Field; +import java.lang.reflect.Method; +import java.util.*; +import javax.swing.*; +import javax.swing.text.AttributeSet; +import javax.swing.text.BadLocationException; +import javax.swing.text.PlainDocument; +public class Calculator { + private final JFrame mainWindow = new JFrame("计算器"); + private final JPanel boxPanel = new JPanel(); + private final JTextField box = new JTextField(); + private final JPanel panel1 = new JPanel(); + private final JButton esc = new JButton("Esc"); + private final JButton backspace = new JButton("<-"); + private final JPanel panel2 = new JPanel(); + private final JButton num0 = new JButton("0"); + private final JButton num1 = new JButton("1"); + private final JButton num2 = new JButton("2"); + private final JButton num3 = new JButton("3"); + private final JButton num4 = new JButton("4"); + private final JButton num5 = new JButton("5"); + private final JButton num6 = new JButton("6"); + private final JButton num7 = new JButton("7"); + private final JButton num8 = new JButton("8"); + private final JButton num9 = new JButton("9"); + private final JButton plus = new JButton("+"); + private final JButton minus = new JButton("-"); + private final JButton multiply = new JButton("*"); + private final JButton divide = new JButton("/"); + private final JButton dot = new JButton("."); + private final JButton equal = new JButton("="); + private final Color defaultBackground = num0.getBackground(); + private final Color enteredBackground = new Color(180,180,180); + + private static final String[] buttonNames = {"num7", "num8", "num9", "multiply", "num4","num5", "num6", "divide","num1", "num2", "num3", "plus", "minus", "num0", "dot", "equal","esc","backspace"}; + private static final String iconBase64 = "iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAADzUlEQVRYR+2Xb2hbVRjGn/fctMvwH+ISEZwoDL9UBkJBIZm2tENh91YQCqKld9A/WzsmdLOriLUtVNlaU4Vhpd1sSeewOBBnkg9lty612TqFougQhh/mUAsu2xjD1bRJzivnJqm3rU2rZkOhBy5cLvd5z3Pec97fOYfgaD7DHAZQRsDDzu8FfL/O4LNCaK2TJ4e/V3EpF9xv7DwH8BMF7CxvqPS8676psQ+u2Qb8VTurwfzx7epc9cPAO2dCwX0ZA3ptJ4g6sgZuEOFNlvRVIQ0RyS0MeklNcTZuNBYKli83QDTmbug9CMjcjwXyIaKJwf3PAPRqfgPMXe5dvQCJXEYKY4BlV2KgLQri0+sG/tsZIMbx4ua+t0jK9woz+ZkoBO5PDLxyD4OOrJIBXAPxKFicKKQBkFQV8OTqZVjQXvMGW4ED6wacGWDucm19+sf0d1/cy0DfouQwn2VQPwmaB3M1APXk2gyYjwAiSsSPL9Nm/so/BSREidoyt4evnD+lb3ps2/M1D3BSm7FXNOP4ZDhY4zTk2E9mBbG/qLG3hCDqBDDw+1DLRE7r0OQ18FMsFHyoMhQvA+E0GOWsictz/fvaQXiBifdubAicdxqYfb/1utD4azBGXXXvNrmKUpfAeE7tKZZxf6dfNz9S2rUZIExvbOw9xKDmbNlEwXIiMXDgThD2A2y4d/XVAuzJVnn85uG23Vpx6ioYgQ0NPSOkkWXpXq8ahGV4on7dfDujXWirVIFEaSwSnK4Mx9nSPZld0zDVqEsAPhYLjdSuMAXfpudd5XfsPfg6gBaAhix9U92f2rUaAH1JMt3hbgrcnRhsnWFGtwMi6kBRL4SYShLPain2EeFDh6EQwIOx0Eh4W5XpW6rNT8J1DizhwIq1nJ8DAHPXv+bAhvoer1rBaiXPDbdcWMqBytCvnSCxxdI9Nc5zpWKI0ubG4tSutQpsDigIMfEJBp4a3+GpyNWyzYHGwEWSIik1CMHpu272H/jB5gBgaysi8fEstASnxJ65oxmGrM0AYTr2WbC0MhLvIEa1BLrHdc9orpbF5kfN4h2NjxDjNwbPE1NSXr50Ye7Tw58jq90evvoGE0tICcvwdv8jDribAq+xoHZ1OLF0T/lSDlSErzQTZImle/csOtpLlLp39xi50dokXGDI3+TAZOTYWFn7UE3qm4m6v+KA9mz91mRkUFvMgQxDlPb/wQFflVlFjJO3j0H23awnFg62LVxOfYZ58RbeipeNzVVUtDn6ydGfFwzYm41uHgL4RRA9eIuycQNgK814eSo88ovq4w/Ej1g/Fj6GKgAAAABJRU5ErkJggg=="; + + public Calculator() { + init(); + setButtonsFont(); + addKeyboardEvent(); + addMouseEvent(); + } + + private void init() { + boxPanel.setLayout(new FlowLayout()); + box.setPreferredSize(new Dimension(350, 30)); + box.setDocument(new LimitedDocument()); + boxPanel.add(box); + panel2.setLayout(new GridLayout(4, 4, 20, 20)); + panel2.setPreferredSize(new Dimension(350, 350)); + + panel1.setLayout(new GridLayout(1,2,20,20)); + panel1.setPreferredSize(new Dimension(350,75)); + panel1.add(esc); + panel1.add(backspace); + + try + { + for(String button:buttonNames) + { + if(!button.equals("esc") && !button.equals("backspace")) + panel2.add((Component) getClass().getDeclaredField(button).get(this)); + } + } + catch (NoSuchFieldException | IllegalAccessException e) + { + e.printStackTrace(); + showMessage("创建界面失败，程序退出！"); + mainWindow.dispose(); + } + + mainWindow.setIconImage(new ImageIcon(Base64.getDecoder().decode(iconBase64)).getImage()); + mainWindow.setLayout(new FlowLayout(FlowLayout.CENTER, 0, 20)); + mainWindow.setVisible(true); + mainWindow.setSize(450, 575); + mainWindow.setLocationRelativeTo(null); + mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); + mainWindow.getContentPane().add(boxPanel); + mainWindow.getContentPane().add(panel1); + mainWindow.getContentPane().add(panel2); + mainWindow.setResizable(false); + + box.requestFocus(); + } + + private void setButtonsFont() { + Font font = new Font("微软雅黑", Font.BOLD, 17); + try { + Method setFontMethod = Class.forName("javax.swing.JButton").getMethod("setFont", Font.class); + for (String buttonName : buttonNames) { + Field buttonField = getClass().getDeclaredField(buttonName); + + buttonField.setAccessible(true); + setFontMethod.invoke(buttonField.get(this), font); + } + } catch (Exception e) { + e.printStackTrace(); + showMessage("字体设置失败，程序退出！"); + mainWindow.dispose(); + } + } + + private void addMouseEvent() { + try { + final Method addEventListenerMethod = Class.forName("javax.swing.JButton").getMethod("addMouseListener", MouseListener.class); + for (String buttonName : buttonNames) { + final Field buttonField = getClass().getDeclaredField(buttonName); + buttonField.setAccessible(true); + addEventListenerMethod.invoke(buttonField.get(this), new MouseListener() { + public void mouseClicked(MouseEvent e) + { + box.requestFocus(); + JButton button = (JButton) e.getSource(); + if(button.equals(equal)) + { + setResult(); + } + else if(button.equals(backspace)) + { + String s = box.getText(); + if(!s.isEmpty()) + { + box.setText(s.substring(0, s.length()-1)); + } + } + else if(button.equals(esc)) + { + box.setText(""); + } + else + { + char c = button.getText().charAt(0); + String boxText = box.getText(); + if (ExpressionHandle.canInput(boxText, c)) + box.setText(boxText + c); + else + showMessage("请点击合法的字符！"); + } + } + + public void mousePressed(MouseEvent mouseEvent) {} + + public void mouseReleased(MouseEvent mouseEvent) {} + + public void mouseEntered(MouseEvent e) { + ((JButton)e.getSource()).setBackground(enteredBackground); + } + public void mouseExited(MouseEvent e) { + ((JButton) e.getSource()).setBackground(defaultBackground); + } + }); + } + } catch (Exception e) { + e.printStackTrace(); + showMessage("反射失败，程序退出！"); + mainWindow.dispose(); + } + } + private void setResult() { + if (!box.getText().isEmpty()){ + ExpressionHandle.setExpression(box.getText()); + try { + showMessage(ExpressionHandle.valid() ? ExpressionHandle.result() : "表达式错误,请重新输入"); + } catch (Exception e) { + showMessage("除数为0,请重新输入"); + } + box.setText(""); + } else { + showMessage("表达式为空,请重新输入"); + } + } + + private void addKeyboardEvent() { + box.addKeyListener(new KeyListener() { + private final Map map = new HashMap<>(); + { + map.put(KeyEvent.VK_0,num0); + map.put(KeyEvent.VK_1,num1); + map.put(KeyEvent.VK_2,num2); + map.put(KeyEvent.VK_3,num3); + map.put(KeyEvent.VK_4,num4); + map.put(KeyEvent.VK_5,num5); + map.put(KeyEvent.VK_6,num6); + map.put(KeyEvent.VK_7,num7); + map.put(KeyEvent.VK_8,num8); + map.put(KeyEvent.VK_9,num9); + map.put(KeyEvent.VK_PLUS,plus); + map.put(KeyEvent.VK_MINUS,minus); + map.put(KeyEvent.VK_MULTIPLY,multiply); + map.put(KeyEvent.VK_SLASH,divide); + map.put(KeyEvent.VK_EQUALS,equal); + map.put(KeyEvent.VK_ENTER,equal); + map.put(KeyEvent.VK_PERIOD,dot); + map.put(KeyEvent.VK_ESCAPE,esc); + map.put(KeyEvent.VK_BACK_SPACE,backspace); + } + public void keyTyped(KeyEvent keyEvent) {} + + public void keyPressed(KeyEvent keyEvent) { + int code = keyEvent.getKeyCode(); + if(keyEvent.isShiftDown()) + { + if(code == KeyEvent.VK_8) + multiply.setBackground(enteredBackground); + else if(code == KeyEvent.VK_EQUALS) + plus.setBackground(enteredBackground); + } + else if(map.containsKey(code)) + { + map.get(code).setBackground(enteredBackground); + if (code == KeyEvent.VK_ENTER) + { + setResult(); + } + else if(code == KeyEvent.VK_ESCAPE) + { + box.setText(""); + } + else if(code == KeyEvent.VK_EQUALS) + { + setResult(); + } + else + { + map.get(keyEvent.getKeyCode()).setBackground(enteredBackground); + } + } + } + public void keyReleased(KeyEvent keyEvent) { + map.forEach((k,v)->v.setBackground(defaultBackground)); + } + }); + } + + public static void showMessage(String message) { + JOptionPane.showMessageDialog(null, message, "提示信息", JOptionPane.INFORMATION_MESSAGE); + } + + public static void main(String[] args) { + new Calculator(); + } + + class LimitedDocument extends PlainDocument { + public void insertString(int offset, String str, AttributeSet attrSet) throws BadLocationException { + if(str.length() == 1) + { + String allowCharAsString = "0123456789+-*/.="; + char c = str.charAt(0); + if (!allowCharAsString.contains(str)){ + Calculator.showMessage("请输入合法字符！"); + return; + } + if(!ExpressionHandle.canInput(box.getText(),c)) { + if(c == '=') + equal.setBackground(defaultBackground); + else if(c == '+') + plus.setBackground(defaultBackground); + else if(c == '-') + minus.setBackground(defaultBackground); + else if(c == '*') + multiply.setBackground(defaultBackground); + else if(c == '/') + divide.setBackground(defaultBackground); + else if(c == '.') + dot.setBackground(defaultBackground); + if(!box.getText().isEmpty()) + Calculator.showMessage("请输入合法字符！"); + return; + } + if(c == '=') + return; + } + super.insertString(offset, str, attrSet); + } + } +} + +class ExpressionHandle { + private static String str; + private static final Deque operators = new ArrayDeque<>(); + private static final Deque operands = new ArrayDeque<>(); + + public static boolean canInput(String s, char c) { + str = s; + if (s == null || s.isEmpty()) + return isDigit(c); + char lastChar = s.charAt(s.length() - 1); + if (isDigit(lastChar)) + return true; + return (!isSign(c) && !isDot(c)) || (!isSign(lastChar) && !isDot(lastChar)); + } + + public static String result() throws Exception { + int len = str.length(); + for (int i = 0; i < len; ++i) { + if (isDigit(i)) { + int i1 = i + 1; + while (i1 < len && (isDigit(i1) || isDot(i1))) + ++i1; + push(Double.parseDouble(str.substring(i, i1))); + i = i1 - 1; + } else { + while (canCalculate(str.charAt(i))) + calculate(); + push(str.charAt(i)); + } + } + while (!empty()) + calculate(); + + String res = String.format("%.5f", getResultNum()); + if (res.contains(".")) { + char[] c = res.toCharArray(); + for (len = c.length - 1; len >= 0; --len) { + if (c[len] != '0') + break; + } + if (c[len] == '.') + --len; + return res.substring(0, len + 1); + } + return res; + } + + private static char getSign() { + if(!operators.isEmpty()) + return operators.peekLast(); + Calculator.showMessage("运行时错误，运算符栈为空"); + throw new RuntimeException("Operators stack is empty."); + } + + private static double getNum() { + if(!operands.isEmpty()) + return operands.peekLast(); + Calculator.showMessage("运行时错误，操作数栈为空"); + throw new RuntimeException("Operators stack is empty."); + } + + private static void popSign() { + operators.removeLast(); + } + + private static void popNum() { + operands.removeLast(); + } + + private static double popAndGetNum() { + double num = getNum(); + popNum(); + return num; + } + + private static char popAndGetSign() { + char sign = getSign(); + popSign(); + return sign; + } + + private static void push(double num) { + operands.addLast(num); + } + + private static void push(char sign) { + operators.addLast(sign); + } + + private static double getResultNum() { + if (!operands.isEmpty()) + return getNum(); + return 0.0; + } + + private static void calculate() throws Exception { + double post = popAndGetNum(); + char sign = popAndGetSign(); + double pre = popAndGetNum(); + double result = 0.0; + + switch (sign) { + case '+': + result = pre + post; + break; + case '-': + result = pre - post; + break; + case '*': + result = pre * post; + break; + case '/': + if (Math.abs(post) < 1e-6) { + throw new Exception("除数为0,请重新输入"); + } else + result = pre / post; + break; + } + push(result); + } + + private static boolean canCalculate(char sign) { + if (operators.isEmpty()) + return false; + char t = getSign(); + switch (t) { + case '+': + case '-': + return sign == '+' || sign == '-'; + case '*': + case '/': + return sign == '+' || sign == '-' || sign == '*' || sign == '/'; + } + return false; + } + + private static boolean empty() { + return operators.isEmpty(); + } + + public static boolean valid() { + if (isSign(0) || isDot(0)) + return false; + int len = str.length(); + for (int i = 0; i < len; ++i) { + if (isSign(i)) { + if (isSign(i + 1) || isDot(i + 1)) + return false; + } else if (isDot(i)) { + if (isSign(i + 1) || isDot(i + 1)) + return false; + } + } + return !isSign(len - 1) && !isDot(len - 1); + } + + public static void setExpression(String s) { + str = s; + operands.clear(); + operators.clear(); + } + + private static boolean isSign(char c) { + return c == '+' || c == '-' || c == '*' || c == '/'; + } + + private static boolean isSign(int index) { + return index < str.length() && isSign(str.charAt(index)); + } + + private static boolean isDot(int index) { + return index < str.length() && isDot(str.charAt(index)); + } + + private static boolean isDot(char c) { + return c == '.'; + } + + private static boolean isDigit(char c) { + return c >= '0' && c <= '9'; + } + + private static boolean isDigit(int index) { + return index < str.length() && isDigit(str.charAt(index)); + } +} \ No newline at end of file -- Gitee From dba073df766642d07696ee4ef31bcca4ba49ebac Mon Sep 17 00:00:00 2001 From: LENOVO Date: Fri, 10 Jun 2022 00:21:15 +0800 Subject: [PATCH 2/3] =?UTF-8?q?=E6=88=91=E6=98=AF=E4=BF=A1=E7=AE=A14?= =?UTF-8?q?=E7=8F=AD30=E5=8F=B7=E5=91=A8=E5=BF=97=E5=98=89=EF=BC=8C?= =?UTF-8?q?=E9=A1=B9=E7=9B=AE=E9=83=A8=E5=88=86=E5=AE=8C=E6=88=90=E8=BF=98?= =?UTF-8?q?=E9=9C=80=E8=A1=A5=E5=85=85=EF=BC=8C=E8=AF=B7=E8=80=81=E5=B8=88?= =?UTF-8?q?=E6=A3=80=E6=9F=A5=E8=AF=84=E9=98=85=E3=80=82?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- src/java2022spring/Calculator.java | 140 +---------------------------- 1 file changed, 1 insertion(+), 139 deletions(-) diff --git a/src/java2022spring/Calculator.java b/src/java2022spring/Calculator.java index dba455c..eb24c40 100644 --- a/src/java2022spring/Calculator.java +++ b/src/java2022spring/Calculator.java @@ -326,142 +326,4 @@ class ExpressionHandle { return res; } - private static char getSign() { - if(!operators.isEmpty()) - return operators.peekLast(); - Calculator.showMessage("运行时错误，运算符栈为空"); - throw new RuntimeException("Operators stack is empty."); - } - - private static double getNum() { - if(!operands.isEmpty()) - return operands.peekLast(); - Calculator.showMessage("运行时错误，操作数栈为空"); - throw new RuntimeException("Operators stack is empty."); - } - - private static void popSign() { - operators.removeLast(); - } - - private static void popNum() { - operands.removeLast(); - } - - private static double popAndGetNum() { - double num = getNum(); - popNum(); - return num; - } - - private static char popAndGetSign() { - char sign = getSign(); - popSign(); - return sign; - } - - private static void push(double num) { - operands.addLast(num); - } - - private static void push(char sign) { - operators.addLast(sign); - } - - private static double getResultNum() { - if (!operands.isEmpty()) - return getNum(); - return 0.0; - } - - private static void calculate() throws Exception { - double post = popAndGetNum(); - char sign = popAndGetSign(); - double pre = popAndGetNum(); - double result = 0.0; - - switch (sign) { - case '+': - result = pre + post; - break; - case '-': - result = pre - post; - break; - case '*': - result = pre * post; - break; - case '/': - if (Math.abs(post) < 1e-6) { - throw new Exception("除数为0,请重新输入"); - } else - result = pre / post; - break; - } - push(result); - } - - private static boolean canCalculate(char sign) { - if (operators.isEmpty()) - return false; - char t = getSign(); - switch (t) { - case '+': - case '-': - return sign == '+' || sign == '-'; - case '*': - case '/': - return sign == '+' || sign == '-' || sign == '*' || sign == '/'; - } - return false; - } - - private static boolean empty() { - return operators.isEmpty(); - } - - public static boolean valid() { - if (isSign(0) || isDot(0)) - return false; - int len = str.length(); - for (int i = 0; i < len; ++i) { - if (isSign(i)) { - if (isSign(i + 1) || isDot(i + 1)) - return false; - } else if (isDot(i)) { - if (isSign(i + 1) || isDot(i + 1)) - return false; - } - } - return !isSign(len - 1) && !isDot(len - 1); - } - - public static void setExpression(String s) { - str = s; - operands.clear(); - operators.clear(); - } - - private static boolean isSign(char c) { - return c == '+' || c == '-' || c == '*' || c == '/'; - } - - private static boolean isSign(int index) { - return index < str.length() && isSign(str.charAt(index)); - } - - private static boolean isDot(int index) { - return index < str.length() && isDot(str.charAt(index)); - } - - private static boolean isDot(char c) { - return c == '.'; - } - - private static boolean isDigit(char c) { - return c >= '0' && c <= '9'; - } - - private static boolean isDigit(int index) { - return index < str.length() && isDigit(str.charAt(index)); - } -} \ No newline at end of file + \ No newline at end of file -- Gitee From 42741228d2bca8ea49fdbdeff434fdb2cb52e1e4 Mon Sep 17 00:00:00 2001 From: LENOVO Date: Fri, 10 Jun 2022 00:26:08 +0800 Subject: [PATCH 3/3] =?UTF-8?q?=E6=88=91=E6=98=AF21=E4=BF=A1=E7=AE=A14?= =?UTF-8?q?=E7=8F=AD=E5=91=A8=E5=BF=97=E5=98=89=EF=BC=8C=E9=A1=B9=E7=9B=AE?= =?UTF-8?q?=E5=B7=B2=E5=AE=8C=E6=88=90=EF=BC=8C=E8=AF=B7=E8=80=81=E5=B8=88?= =?UTF-8?q?=E6=9F=A5=E9=98=85?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- src/java2022spring/Calculator.java | 138 +++++++++++++++++++++++++++++ 1 file changed, 138 insertions(+) diff --git a/src/java2022spring/Calculator.java b/src/java2022spring/Calculator.java index eb24c40..62a907f 100644 --- a/src/java2022spring/Calculator.java +++ b/src/java2022spring/Calculator.java @@ -325,5 +325,143 @@ class ExpressionHandle { } return res; } + private static char getSign() { + if(!operators.isEmpty()) + return operators.peekLast(); + Calculator.showMessage("运行时错误，运算符栈为空"); + throw new RuntimeException("Operators stack is empty."); + } + + private static double getNum() { + if(!operands.isEmpty()) + return operands.peekLast(); + Calculator.showMessage("运行时错误，操作数栈为空"); + throw new RuntimeException("Operators stack is empty."); + } + + private static void popSign() { + operators.removeLast(); + } + + private static void popNum() { + operands.removeLast(); + } + + private static double popAndGetNum() { + double num = getNum(); + popNum(); + return num; + } + + private static char popAndGetSign() { + char sign = getSign(); + popSign(); + return sign; + } + + private static void push(double num) { + operands.addLast(num); + } + + private static void push(char sign) { + operators.addLast(sign); + } + + private static double getResultNum() { + if (!operands.isEmpty()) + return getNum(); + return 0.0; + } + + private static void calculate() throws Exception { + double post = popAndGetNum(); + char sign = popAndGetSign(); + double pre = popAndGetNum(); + double result = 0.0; + + switch (sign) { + case '+': + result = pre + post; + break; + case '-': + result = pre - post; + break; + case '*': + result = pre * post; + break; + case '/': + if (Math.abs(post) < 1e-6) { + throw new Exception("除数为0,请重新输入"); + } else + result = pre / post; + break; + } + push(result); + } + + private static boolean canCalculate(char sign) { + if (operators.isEmpty()) + return false; + char t = getSign(); + switch (t) { + case '+': + case '-': + return sign == '+' || sign == '-'; + case '*': + case '/': + return sign == '+' || sign == '-' || sign == '*' || sign == '/'; + } + return false; + } + private static boolean empty() { + return operators.isEmpty(); + } + + public static boolean valid() { + if (isSign(0) || isDot(0)) + return false; + int len = str.length(); + for (int i = 0; i < len; ++i) { + if (isSign(i)) { + if (isSign(i + 1) || isDot(i + 1)) + return false; + } else if (isDot(i)) { + if (isSign(i + 1) || isDot(i + 1)) + return false; + } + } + return !isSign(len - 1) && !isDot(len - 1); + } + + public static void setExpression(String s) { + str = s; + operands.clear(); + operators.clear(); + } + + private static boolean isSign(char c) { + return c == '+' || c == '-' || c == '*' || c == '/'; + } + + private static boolean isSign(int index) { + return index < str.length() && isSign(str.charAt(index)); + } + + private static boolean isDot(int index) { + return index < str.length() && isDot(str.charAt(index)); + } + + private static boolean isDot(char c) { + return c == '.'; + } + + private static boolean isDigit(char c) { + return c >= '0' && c <= '9'; + } + + private static boolean isDigit(int index) { + return index < str.length() && isDigit(str.charAt(index)); + } +} \ No newline at end of file -- Gitee