1.背景

前两天为了赶速度，自己很快实现了如题java老师布置的作业，并在csdn上写了博客，记录学习过程，原博客链接为:http://blog.csdn.net/u010043538/article/details/12765527。但是很快有无私的网友指出了其中一个显然的错误：没有考虑除数为0的情况。虽然java初学，不过错就是错，没有啥理由。自己以后写老师作业，会尽可能深进去，把已经自学过的内容体现出来，而不是跟老师上课的内容来写代码。在此基础上，尽可能保证快速解决问题。

此次改进修正了错误：没有考虑除数为0的情况。并对程序的封装性做了一定程度的改进。

2.具体代码(附注释)

package Four;
/**
 * @author Kun Sun
 * @Date： 2013.10.17
 */

public class Complex { // 复数类
	double real;  // 实部
	double image; // 虚部

	Complex(double real,double image){ // 带参数的构造方法
		this.real = real;
		this.image = image;
	}

	public Complex() {
		// TODO Auto-generated constructor stub
	}

	public double getReal() {
		return real;
	}

	public void setReal(double real) {
		this.real = real;
	}

	public double getImage() {
		return image;
	}

	public void setImage(double image) {
		this.image = image;
	}
	
	Complex add(Complex a){ // 复数相加
		double real2 = a.getReal();
		double image2 = a.getImage();
		double newReal = real + real2;
		double newImage = image + image2;
		Complex result = new Complex(newReal,newImage);
		return result;
	}
	
	Complex sub(Complex a){ // 复数相减
		double real2 = a.getReal();
		double image2 = a.getImage();
		double newReal = real - real2;
		double newImage = image - image2;
		Complex result = new Complex(newReal,newImage);
		return result;
	}
	
	Complex mul(Complex a){ // 复数相乘
		double real2 = a.getReal();
		double image2 = a.getImage();
		double newReal = real*real2 - image*image2;
		double newImage = image*real2 + real*image2;
		Complex result = new Complex(newReal,newImage);
		return result;
	}
	
	Complex div(Complex a){ // 复数相除
		double real2 = a.getReal();
		double image2 = a.getImage();
	    double newReal = (real*real2 + image*image2)/(real2*real2 + image2*image2);
		double newImage = (image*real2 - real*image2)/(real2*real2 + image2*image2);
		Complex result = new Complex(newReal,newImage);
		return result;
	}
	
	public void print(){ // 用于格式化输出
		if(image > 0){
			System.out.println(real + " + " + image + "i");
		}else if(image < 0){
			System.out.println(real + "" + image + "i");
		}else{
			System.out.println(real);
		}
	}
	
	// 封装了具体运算，主要为对输入进行转换，对输出封装
	public static void talk(String data1_1,String data1_2,String data2_1,String data2_2,String operation){
		
        // 以下语句为格式转换     
		double dat1_1 = Double.parseDouble(data1_1); // 把string型实部转为double型
		double dat1_2 = Double.parseDouble(data1_2.substring(0,data1_2.length()-1));// 把去除"i"的string型虚部转为double型
		double dat2_1 = Double.parseDouble(data2_1);// 把string型实部转为double型
		double dat2_2 = Double.parseDouble(data2_2.substring(0,data2_2.length()-1));// 把去除"i"的string型虚部转为double型
		
		Complex num1 = new Complex(dat1_1,dat1_2);
		Complex num2 = new Complex(dat2_1,dat2_2);
		
		Complex result;
		int a,b;
		
		if(operation.equals("+")){ // 两数相加
 			result = num1.add(num2);
 			result.print();
		}
		
		if(operation.equals("-")){ // 两数相减
 			result = num1.sub(num2);
			result.print();
		}
		
		if(operation.equals("*")){ // 两数相乘
 			result = num1.mul(num2);
			result.print();
		}
		
		if(operation.equals("/")){ // 两数相除
			
			if(num2.real * num2.real + num2.image*num2.image != 0){
	 			result = num1.div(num2);
	 			result.print();
			}else{
				System.out.println("运算出错,除数运算中除数不能为0,请用户重新输入!");
			}
		}
	}
}

package Four;

import java.util.Scanner;

/**
 * @author Kun Sun
 * @Date： 2013.10.17
 */
public class MainClass { // 用于测试复数类

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Complex complex = new Complex();
		
		// 以下测试中的talk()中的解释为
		// talk(string data1_1,string data1_2,string data2_1,string data2_2,string operation);
		// data1_1,data1_2依次为第一个复数的实部和虚部
		// data2_1,data2_2依次为第二个复数的实部和虚部
		// operation为两个复数运算的操作符,每种测试都做加减乘除
		
		System.out.println("测试1:-------------------------");  // 一般测试
		complex.talk("5", "4i", "3", "6i", "+");
		complex.talk("5", "4i", "3", "6i", "-");
		complex.talk("5", "4i", "3", "6i", "*");
		complex.talk("5", "4i", "3", "6i", "/");
		
		System.out.println("\n测试2:-------------------------"); // 包含负数测试
	    complex.talk("-2","4i", "5", "-8i","+");
	    complex.talk("-2","4i", "5", "-8i","-");
	    complex.talk("-2","4i", "5", "-8i","*");
	    complex.talk("-2","4i", "5", "-8i","/");
	    
	    System.out.println("\n测试3:-------------------------"); // 包含小数测试
	    complex.talk("-1.2","3.1i","4.3","-6.5i","+");
	    complex.talk("-1.2","3.1i","4.3","-6.5i","-");
	    complex.talk("-1.2","3.1i","4.3","-6.5i","*");
	    complex.talk("-1.2","3.1i","4.3","-6.5i","/");
	    
	    System.out.println("\n测试4:-------------------------"); // 包含除数为0测试
	    complex.talk("5", "4i", "0", "0i", "+");
	    complex.talk("5", "4i", "0", "0i", "-");
	    complex.talk("5", "4i", "0", "0i", "*");
	    complex.talk("5", "4i", "0", "0i", "/");
	}
}