终极版声明复数类，成员变量包括实部和虚部，成员方法包括实现由字符串构造复数、复数加法、减法，字符串描述、比较

实名感谢尚梦川大佬教会我正则表达式！！！！！！！！！！！！！！！！！！！！！！！！！！

输入的必须是正确答案，主要是尝试正则表达式。 看不懂的童邪慎用。优化也不是特别好，但是看懂了比较舒服。

有错误欢迎指正

import java.util.Scanner;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class Complextest {

public float real,vir;

public static int count=0;

public static String Input()

{

    Scanner in = new Scanner(System.in);

            count++;

    System.out.println("请输入第"+count+"个复数:");

    String res= in.next();

    return res;

}

    public Complextest (String str)

    {

        if(str.equals("i")||str.equals("+i"))

        {

            this.real=0;

            this.vir =1;

        }

        else if(str.equals("-i"))

        {

            this.real=0;

            this.vir =-1;

        }

        else{

        String a = "^([-+]?)(\\d+|\\d+\\.\\d+)$";//只有实部的匹配

        String bi =   "^([-+]?)(\\d+|\\d+\\.\\d+)?(i+)$";//只虚部的匹配

        String a_bi = "^([-+]?)(\\d+|\\d+\\.\\d+)([-+]+)(\\d+|\\d+\\.\\d+)(i+)$";//都有

        String a_i =  "^([-+]?)(\\d+|\\d+\\.\\d+)([-+]+)(i+)$";

        Pattern fora = Pattern.compile(a);

        Pattern forbi = Pattern.compile(bi);

        Pattern fora_bi = Pattern.compile(a_bi);

        Pattern fora_i = Pattern.compile(a_i);

        Matcher toa= fora.matcher(str);

        Matcher tobi= forbi.matcher(str);

        Matcher toa_bi= fora_bi.matcher(str);

        Matcher toa_i= fora_i.matcher(str);

        if(toa_i.find())//([-+]?)(\\\\d+|\\\\d+\\\\.\\\\d+)([-+]+)(i+)

        {

            this.real = Float.parseFloat(toa_i.group(1)+toa_i.group(2));

            this.vir = 1;

            if(toa_i.group(3).equals("-"))

            {

                this.vir*=-1;

            }

        }

        if(toa.find())//只匹配实部

        {

            this.real = Float.parseFloat(toa.group(0));

            this.vir = 0;

        }else if(tobi.find())//只匹配虚部"([-+]?)(\\d+|\\d+\\.\\d+)(i+)";

        {



            this.real=0;

            this.vir=Float.parseFloat(tobi.group(1)+tobi.group(2));

        }

        if(toa_bi.find())//([-+]?)(\\d+|\\d+\\.\\d+)([-+]+)(\\d+|\\d+\\.\\d+)(i+)

        {



            this.real = Float.parseFloat(toa_bi.group(1)+toa_bi.group(2));

            if(toa_bi.group(4).length()==0)

            {

                this.vir=1;

                if(toa_bi.group(3)=="+")

                {

                    this.vir*=-1;

                }

            }else {

                this.vir=Float.parseFloat(toa_bi.group(3)+toa_bi.group(4));

            }

        }

        }

        System.out.print("你输入的复数:");

        sayResult(this.real,this.vir);

    }

    public void add(Complextest other)//加法

    {

        float sum_Real,sum_Vir;

        sum_Real=this.real+other.real;

        sum_Vir=this.vir+other.vir;

        System.out.print("和:");

        sayResult(sum_Real,sum_Vir);

    }

    public void lenth(Complextest other)//长度

    {

        float x_len,y_len;

        x_len=this.real-other.real;

        y_len=this.vir-other.vir;

        System.out.println("长度是"+String.format("%.2f", Math.sqrt(x_len*x_len+y_len*y_len)));

    }

    public boolean equls(Complextest other)

    {

        System.out.print("是否相等:");

        return this==other||Math.abs(this.real-other.real)<0.001&&Math.abs(this.vir-other.vir)<0.001;

    }

    public void diff(Complextest other)//减法

    {

        float diff_Real,diff_Vir;

        diff_Real=this.real-other.real;

        diff_Vir=this.vir-other.vir;

        System.out.print("差:");

        sayResult(diff_Real,diff_Vir);

    }

    public void sayResult(float Real_,float Vir_)

    {

        StringBuffer put = new StringBuffer();

        String str=String.valueOf(Real_);

        if(Real_!=0)//实部存在

        {

            put.append(str);

            if(Vir_!=0)//等于0就不管

            {

                if(Vir_>0)

                {

                    if(Vir_==1)//虚部为1

                    {

                        put.append("+i");

                    }else {

                        put.append("+"+Vir_+"i");

                    }

                } else if(Vir_<0)

                {

                    if(Vir_==-1)//虚部为-1

                    {

                        put.append("-i");

                    }else {

                        put.append(Vir_+"i");

                    }

                }

            }

        }else//不存在实部

        {

            if(Vir_!=0)//只有虚部

            {

                if(Vir_==-1)

                {

                    put.append("-i");

                }else if(Vir_==1)

                {

                    put.append("i");

                }else

                {

                    put.append(Vir_+"i");

                }

            }else//虚部都没有

            {

                put.append("0");

            }

        }

        System.out.println(put);

    }

    public static void main(String[] args) {

        String str;

        str = Input(); 

        Complextest first = new Complextest(str); 

           str = Input(); 

        Complextest second = new Complextest(str);    

        first.add(second);

        first.diff(second);

        first.lenth(second);

        System.out.println(first.equls(second));

    }

}