java - 数组 "missing return statement"出现 1 个错误

Question

import javax.swing.JOptionPane;

public class Mate {

double suma (double x1,double x2)
    {return x1+x2;}

double suma (double x1,double x2,double x3)
    {return x1+x2+x3;}

double suma (int num [ ])

    {int i=num.length;
     int j=0;
     int s=0;

for(j=0;j < i;j++)

{return (double)(s);}}} // here appears the error "missing return statement"

class AplicacionMate

{public static void main (String arg [])

    {int n[ ]={5,4,3,2,1};
     double r=0.0;
     Mate m=new Mate ( );
     r=m.suma(5,4);
     JOptionPane.showMessageDialog(null,"La suma 1="+r);
     r=m.suma(5,5,4);
     JOptionPane.showMessageDialog(null,"La suma 2="+r);
     r=m.suma(n);
     JOptionPane.showMessageDialog(null,"La suma del arreglo="+r);
     System.exit(0);}}

Answer 1

我冒昧地格式化了您的代码。这是该方法的样子:

double suma (int num [ ]) {
    int i=num.length;
    int j=0;
    int s=0;

    for(j=0;j < i;j++) {
        return (double)(s);
    }
}

我怀疑您试图编写一个 sum-method，从一个 stub 开始，但没有让它编译。这可能是您的想法:

double suma (int num [ ]) {
    int i=num.length;
    int j=0;
    int s=0;

    for(j=0;j < i;j++) {
        // here you probably want s += num[j];
    }

    return (double)(s);

}

---

Java 编译器只能在非常简单的情况下推断语句(例如 return)是可达的。 (为了说明:此方法确实编译。但仍然不是很有用!)

double suma (int num [ ]) {
    int i=num.length;
    int j=0;
    int s=0;

    for(j=0; true; j++) {
        return (double)(s);
    }
}