界面：
若存在Bug，概不负责，请谨慎使用（^-^）。正常使用没问题，还有些功能在修复...
仅供参考！
源代码：
package lianxi; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.ArrayList; import java.util.Queue; import java.util.Stack; import java.util.Vector; import javax.swing.*; import java.util.EventObject.*; import java.io.*; import java.math.BigDecimal; public class Caculator extends JFrame { String input = ""; String cs = " "; JTextField tf = new JTextField(); JTextArea text = new JTextArea(); JPanel panel1 = new JPanel(); JPanel contentPane = new JPanel(); StringBuffer strBuf = new StringBuffer(); JButton[] jbs = new JButton[20]; JButton save = new JButton("保存"); JButton copy = new JButton("复制"); JButton clear = new JButton("清除"); JScrollPane js = new JScrollPane(text);// 滚动条 public Caculator() { JFrame frame = new JFrame("计算器"); // 窗框 tf.setHorizontalAlignment(JTextField.RIGHT);// 右对齐 // tf.setEditable(false);//文本框禁止编辑 tf.setBounds(0, 10, 350, 20); js.setBounds(360, 5, 200, 70); panel1.setLayout(new GridLayout(4, 5, 0, 0)); panel1.setBounds(0, 30, 350, 80); save.setBounds(360, 80, 60, 30); copy.setBounds(430, 80, 60, 30); clear.setBounds(500, 80, 60, 30); contentPane.setLayout(null); contentPane.add(tf); contentPane.add(panel1); contentPane.add(js); contentPane.add(save); contentPane.add(copy); contentPane.add(clear); frame.setContentPane(contentPane); ArrayList<String> strArray = new ArrayList<String>(); strArray.add("1"); strArray.add("2"); strArray.add("3"); strArray.add("+"); strArray.add("c"); strArray.add("4"); strArray.add("5"); strArray.add("6"); strArray.add("-"); strArray.add("退格"); strArray.add("7"); strArray.add("8"); strArray.add("9"); strArray.add("*"); strArray.add("√");strArray.add("0"); strArray.add(".");strArray.add("%"); strArray.add("/"); strArray.add("="); for (int i = 0; i < jbs.length; i++) { jbs[i] = new JButton(strArray.get(i) + ""); jbs[i].setSize(70, 30); panel1.add(jbs[i]); jbs[i].addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent arg0) { // TODO Auto-generated method stub String s = arg0.getActionCommand(); if (s.equals("=") == false) {// 不为等于时全显示 cs += s; } if (s.equals("c")) { cs = " "; input = ""; } if (s.equals("退格")) { int m = input.length(); int flag = 0; for (int i = 0; i < cs.length(); i++) { if (tf.getText().equals("") && cs.charAt(i) == '退') { flag = 1; cs = " "; return; } } if (flag == 0) { if (m == 1) { input = input.substring(0, 0);// 防止输入一个数字就退格 tf.setText(""); return; } if (input.charAt(m - 2) == '+' || input.charAt(m - 2) == '-' || input.charAt(m - 2) == '*' || input.charAt(m - 2) == '/' || input.charAt(m - 2) == '%' || input.charAt(m - 2) == '√') { input = input.substring(0, input.length() - 3); } else input = input.substring(0, input.length() - 1); cs = cs.substring(0, cs.length() - 3); } } tf.setText(cs); if (s.equals("+") || s.equals("-") || s.equals("*") || s.equals("/") || s.equals("%")|| s.equals("√")) { input += " " + s + " "; } else if (s.equals("=")) { String input1 = ""; String show = ""; for (int i = 0; i < input.length(); i++) { if (input.charAt(i) != 'c') { input1 += input.charAt(i); } } show = input1 + "=" + " " + compute(input); strBuf.append(show + "\n"); text.setText(strBuf.toString()); } else if (s.equals("退格") == false) { /*这里如果改成if (s.equals("退格") == false||s.equals("c") == false) 的话，那么当输入"c"时逻辑判断第一个成立，逻辑短路，条件成立。那么就将"c"假如到了input 因此，在compute计算函数中才将"c"取出*/ input += s; } } }); save.addActionListener(new ActionListener() { // 按钮动作事件处理 public void actionPerformed(ActionEvent e) { BufferedWriter out = null; int flag=0; File file = new File("d://writeFile.txt"); try { out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file, true))); out.append(text.getText()); out.write(123); } catch (Exception e0) { e0.printStackTrace(); } finally { try { out.flush(); out.close(); } catch (IOException e1) { e1.printStackTrace(); } } } }); copy.addActionListener(new ActionListener() { // 按钮动作事件处理 public void actionPerformed(ActionEvent e) { text.copy();//这个没用 } }); clear.addActionListener(new ActionListener() { // 按钮动作事件处理 public void actionPerformed(ActionEvent e) { text.setText(""); strBuf.setLength(0); // 清空strBuf中的数据 } }); } frame.setBounds(100, 200, 600, 150); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); frame.setResizable(false);// 窗口大小不可改变 } public static void main(String[] args) {// static new Caculator(); } public static int sq(int n){//求根号时先求整数 if( n == 1){ return 1; } int tmp = 0; for(int i=1;i<=n/2+1;i++){ if(i*i == n){ tmp = i; break; } if(i*i > n){ tmp = i-1; break; } } return tmp; } public static double[] sc(int m){ //m==3保留三位小数 double[] arr = new double[m]; int num = 0; while(num != m){ double f = 1; for(int i=0;i<=num;i++){ f = f*10; } arr[num] = 1/f;//arr[0]=0.1 f==10、arr[1]=0.01 f==100、arr[2]=0.001 f==1000 num++; } return arr; } public static double sb(int n, double j, double[] arr){ double tmp = j; for(int p=0;p<arr.length;p++){ if(p>0){ j = tmp;//计算过后的值（整数位+小数位的和，赋值给j，下面继续运算） } for(int i=1;i<=9;i++){//小数位只有九位{0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9} tmp = i*arr[p]+j; if(tmp*tmp == n){ return tmp; } if(tmp*tmp >n){ //避免丢失精度 BigDecimal c1 = new BigDecimal(Double.toString(tmp)); BigDecimal c2 = new BigDecimal(Double.toString(arr[p])); tmp = c1.subtract(c2).doubleValue(); break; } } } return tmp; } private String compute(String input)// 即1237 的 样例 { String str[]; String inputnew = ""; double dou; for (int i = 0; i < input.length(); i++) { if (input.charAt(i) != 'c') { inputnew += input.charAt(i); } } str = inputnew.split(" ");// 以空格分隔 if (str[1].compareTo("√") == 0) { String str1=""; for(int j=2;j<str.length;j++) { str1+=str[j]; } double ans1 = Double.parseDouble(str1);//这里转化一下 if(ans1==0) return "false"; if(ans1==1) return String.valueOf(ans1); dou=sb((int)ans1,sq((int)ans1), sc(3)); String result1 = String.valueOf(dou); return result1; } //1+2+3 Stack<Double> s = new Stack<Double>(); double m = Double.parseDouble(str[0]);//第一个为数字,奇数为运算符,偶数为操作数 s.push(m); for (int i = 1; i < str.length; i++) { if (i % 2 == 1) { if (str[i].compareTo("+") == 0) { double help = Double.parseDouble(str[i + 1]); s.push(help); } if (str[i].compareTo("-") == 0) { double help = Double.parseDouble(str[i + 1]); s.push(-help); } if (str[i].compareTo("*") == 0) {//1*2 double help = Double.parseDouble(str[i + 1]); double ans = s.peek();// 取出栈顶元素 s.pop();// 消栈 ans *= help; s.push(ans); } if (str[i].compareTo("/") == 0) { double help = Double.parseDouble(str[i + 1]); double ans = s.peek(); s.pop(); ans /= help; s.push(ans); } if (str[i].compareTo("%") == 0) { double help = Double.parseDouble(str[i + 1]); double ans = s.peek(); s.pop(); ans %= help; s.push(ans); } } } double ans = 0d; while (!s.isEmpty()) { ans += s.peek(); s.pop(); } String result = String.valueOf(ans); return result; } }
