java - 在java程序中使用方法

Question

在将程序划分为方法时(特别是主方法和执行所有计算的另一个方法等)，我遇到了麻烦。我不确定划分现有代码以创建新方法的正确方法。我的程序也写入文件。

当我编译代码时，我收到一条错误消息

File: F:\COMPSCI 12\java1.java [line: 37] Error: F:\COMPSCI 12\java1.java:37: missing return statement

但我已经有一个返回声明。

我是否正确使用了这些方法？或者出了什么问题？谢谢

没有方法的原始代码

    import java.io.*;

public class java1
{
  public static void main (String [] args) throws IOException
  {
    //int variables are declared
    int numpoints = 100, dimension = 2, length = 100;//numpoints is set to 100, dimension is set to 2, length is set to 100

    PrintWriter fileOut = new PrintWriter (new FileWriter ("arrayNumPoints.txt"));

    //arays are declared/initialized
    double [] lengthscale = new double [dimension];
    double [][] locations = new double [numpoints][dimension];

    for (int a = 0; a < dimension; a++){//for loop runs while a is less than dimension
      lengthscale[a] = length;//stores array
    }//end for loop

    for (int x=0; x < numpoints; x++){//for loop runs while x is less than numpoints
      for (int y=0; y < dimension; y++){//nested for loop runs while y is less than dimension
        locations [x][y]= (2 * Math.random() - 1) * lengthscale[y];//creates the range and choses random point within it

        fileOut.println( locations[x][y] + ", ");//prints out coordinate

      }//end nested for loop
    }//end for loop

    fileOut.close ();
  }//end main method
}//end cass

相同的代码但使用方法

 import java.io.*;

public class J4_2_MultiDimensionalArray7
{
  public static void main (String [] args) throws IOException
  {
    int numpoints = 100, dimension = 2, length = 100;//numpoints is set to 100, dimension is set to 2, length is set to 100

    //arrays are initializewd and declared
    double [] lengthscale = new double [dimension];
    double [][] locations = new double [numpoints][dimension];

    PrintWriter fileOut = new PrintWriter (new FileWriter ("arrayNumPoints.txt"));


    for(int m=0; m <length; m++){//for loop
      fileOut.println(java.util.Arrays.toString(locations[m]) + ", ");
    }
  }//end main

    public static Double writefile(Double locations[][], Double lengthscale[], int dimension, int numpoints, Double length)throws IOException
    {


    for (int a = 0; a < dimension; a++){//for loop runs while a is less than dimension
      lengthscale[a] = length;//stores array
    }//end for loop

    for (int x=0; x < numpoints; x++){//for loop runs while x is less than numpoints
      for (int y=0; y < dimension; y++){//nested for loop runs while y is less than dimension
        locations [x][y]= (2 * Math.random() - 1) * lengthscale[y];//creates the range and choses random point within it

      return locations[x][y];//returns the value of locations
      }//end nested for loop

    }//end for loop

    fileOut.close ();//close file
  }//end writefile methos
}//end cass

Answer 1

假设numpoints == 0。您的代码会到达 return 语句吗？

在另一种情况下，如果您的函数确实返回，fileOut.close();会被调用吗？

Java 认识到存在一种可能无法到达 return 语句的情况，并且会表现得好像您没有这种情况一样。要解决此问题，您应该在函数末尾有一个“默认”返回语句，以处理未进入循环的边缘情况。

Im not sure on the proper way to divide up my existing code to create a new method.

这实际上取决于您以及代码的作用，但有一些指导原则:

• 方法太长难以理解？将其分为几种方法。
• 您是否在编写“重复代码”？也许这应该放在一个方法中。
• 像写入文件这样的事情是一个离散的操作单元。换句话说，与程序其余部分的逻辑分开。因此应该将其分离为自己的方法。
• 等等