import javax.swing.*;

import java.awt.*;

/**

 * 计算器

 * @author paul

 * 2019.11.25 21：43

 * */

public class MyCalculator {

    private String str="";//输入输出框内容

    private JTextField text_input;//输出框

    private JPanel jp_bottomArea;//按钮区域

    private String []addsButtonString={"1","2","3","+","4","5","6","-","7","8","9","*",".","0","求根","/","=","取反","AC"};

    public MyCalculator(){

        //初始化窗体

        JFrame frame=new JFrame("计算器");

        Container c=frame.getContentPane();

        c.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));//设置排布方式为Y轴排列

        frame.setLocation(200,300);//设置位置

        frame.setVisible(true);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        text_input=new JTextField(30);

        text_input.setHorizontalAlignment(JTextField.RIGHT);

        JPanel jPanel=new JPanel(new GridLayout(1,1,10,10));

        jPanel.add(text_input);

        c.add(jPanel);

        GridBagLayout gridBagLayout=new GridBagLayout();

        GridBagConstraints cs=new GridBagConstraints();

        jp_bottomArea=new JPanel();

        jp_bottomArea.setLayout(gridBagLayout);

        for(int i=0;i<addsButtonString.length;i++){

            if((i+1)%4==0){

                cs.gridwidth=GridBagConstraints.REMAINDER;

            }else if(addsButtonString[i].equals("=")){

                cs.gridwidth=2;

            }else {

                cs.fill=GridBagConstraints.BOTH;

                cs.weightx=1.0;

                cs.gridwidth=1;

            }

            JButton btn = new JButton(addsButtonString[i]);

            gridBagLayout.setConstraints(btn,cs);

            btn.addActionListener(e -> {

                String command = e.getActionCommand();

                setShowTextFiledNew(command);

            });

            jp_bottomArea.add(btn);

        }

        c.add(jp_bottomArea);

        frame.pack();

    }

    /**

     * 设置显示内容窗格

     * @param command 按钮点击命令

     * 如果按下等于，则执行计算

     * 如果按下运算符，则格式为 空格+运算符+空格

     * 如果按下时数字，则直接拼接

     * */

    public void setShowTextFiledNew(String command){

       if(command.equals("=")){

           str=getResult(str);

       }else if(command.equals("+")||command.equals("-")||command.equals("*")||command.equals("/")||command.equals("求根")||command.equals("取反")){

           str=str+" "+command+" ";

       }else if(command.equals("AC")){

           str="";

       }else {

           str=str+command;

       }

       text_input.setText(str);

    }

    /**

     * 计算

     * @param str 需要计算的字符串

     * 根据空格进行分割成字符串数组

     * 然后判断是哪种类型的运算符并进行计算

     * 通过一个result来存放最终结果

     * */

    public String getResult(String str){

        Double result=0.0;

        String []need_to_do=str.split(" ");

        for(int i=0;i<need_to_do.length;i++){

            switch (need_to_do[i]){

                case "+":

                    result=result+(Double.parseDouble(need_to_do[i-1])+Double.parseDouble(need_to_do[i+1]));

                    break;

                case "-":

                    result=result+(Double.parseDouble(need_to_do[i-1])-Double.parseDouble(need_to_do[i+1]));

                    break;

                case "*":

                    result=result+(Double.parseDouble(need_to_do[i-1])*Double.parseDouble(need_to_do[i+1]));

                    break;

                case "/":

                    result=result+(Double.parseDouble(need_to_do[i-1])/Double.parseDouble(need_to_do[i+1]));

                    break;

                case "求根":

                    result=result+(Math.sqrt(Double.parseDouble(need_to_do[i-1])));

                    break;

                case "取反":

                    result=result+(-Double.parseDouble(need_to_do[i-1]));

                    break;

            }

        }

        return result+"";

    }

    public static void main(String[] args) {

        new MyCalculator();

    }

}