设计模式之 使用静态工厂模式代替构造函数(Java)

设有一个

package com.stephen.javatest02;

public class Complex {
private double re;
private double im;

private Complex(double re, double im) //注意这里用private， 不让使用者直接来new生成
{
this.re = re;
this.im = im;
}

public void printRe()
{
System.out.println("re=" + this.re );
}
public void printIm()
{
System.out.println("im=" + this.im );
}

public static Complex CreateByReIm(double re, double im)//同样参数, 如果使用构造函数来构造容易混
{
return new Complex(re, im);
}

public static Complex CreateByPolar(double r, double theta)//同样参数, 如果使用构造函数来构造容易混
{
return new Complex(r*Math.cos(theta), r*Math.sin(theta));
}
}

调用实例：
Complex mycom = Complex.CreateByReIm(3.1, 5.2);
mycom.printRe();
mycom.printIm();
Complex mycom2 = Complex.CreateByPolar(6.7, 8.9);
mycom2.printRe();
mycom2.printIm();