Java 局部变量real可能尚未初始化

我已经为复数编写了complex.java代码。但它在eclipse上给出了错误“局部变量real可能尚未初始化”。不知道怎么了。代码如下。任何帮助都将不胜感激

import java.lang.Math; 

public class Complex { 
    public double real; 
    public double comp; 

    Complex(double real, double comp) {  
    this.real = real; 
    this.comp = comp; 
    }

    Complex() { 
    this.real = 0; 
    this.comp = 0;
    }


    public double getReal() {
        return real;
    }

    public double getImg() {
        return comp;
    }


    public Complex add(Complex a) { 
        return new Complex(a.getReal() + this.real, a.getImg() + this.comp);
    }


    public static Complex add(Complex a, Complex b) { 
        double real = a.real + b.real;
        double comp = a.comp + b.comp;
        Complex sum = new Complex(real, comp);
        return sum;
    }

    public double getABS() { 
        return Math.sqrt(real*real + comp*comp);
    }

    public double getABSSqr() { /* get the squre of absolute */
        return (real*real + comp*comp);
    }


    public Complex mul(Complex a) { 
        return new Complex(a.getReal()*this.real-a.getImg()*this.comp, a.getReal()*this.comp+this.real*a.getImg());
    }

    public static Complex mul(Complex a, Complex b) { 
        double real = a.real*b.real-a.comp*b.comp;
        double comp = a.real*b.comp+b.real*a.comp;
        Complex mul = new Complex(real, comp);
        return mul;
    }

    public Complex squre() { 
        double real = real*real-comp*comp; //THIS IS WHERE ERROR APPEARS FOR real*real
        double comp = 2*real*comp;  //THIS IS WHERE ERROR APPEARS FOR comp                  
        Complex squre = new Complex(real, comp);
        return squre;
    }   

    public void display() { 
    System.out.println(this.real + " + " + this.comp + "j");
    }
}

---

您需要在该语句的右侧使用

this.real

和

this.comp

。这是因为在该范围内有同名的局部变量。要将这些变量与实例变量区分开来，需要使用

this

double real = this.real*this.real-this.comp*this.comp;
double comp = 2*real*this.comp; // this.comp refers the instance variable comp and real refers the real declared in the previous line

因此，如果您只给出

real

，它将尝试使用左侧本身的

real

，它尚未初始化，因此会出现错误

    double real = real*real-comp*comp; //THIS IS WHERE ERROR APPEARS FOR real*real
    double comp = 2*real*comp;  //THIS IS WHERE ERROR APPEARS FOR comp  

---

这是指等式左侧的同一声明变量。您需要为局部变量使用不同的名称，或者在右侧使用this.real*this.real。

好问题！行中：

double real = real*real-comp*comp;

real*real

表达式中引用的实变量 实际上是您刚才声明的本地

real

变量，而不是

real

如您所想，对象的字段。局部变量优先 就范围而言。如果要引用该字段，则需要使用：

this.real

明确说明您所谈论的范围

例如：

double real = this.real * this.real - this.comp * this.comp;
double comp = 2 * this.real * this.comp;

或者，您可以通过为局部变量使用不同的名称来避免问题，这样编译器就不会混淆：

double r = real * real - comp * comp;
double c = 2 * real * comp;
return new Complex(r, c);

或者，您可以删除临时变量并将计算放在一行上：

public Complex square() { 
    return new Complex(real * real - comp * comp, 2 * real * comp);
}

---

如果您只是阅读错误语句，您认为这意味着什么？因为这是一个不可变的对象（好主意！）为了清晰起见，最好将real和comp这两个字段设置为final。