java如果没有构造器，我怎么能让这段代码实现相同的功能？

Question

我对编程非常陌生，我正在尝试修改我在网上找到的堆算法。根据前面的问题，我能够让代码与PrintWriter一起工作，但是当尝试在另一个类中将此函数用作方法时，由于构造函数的原因，我得到了一个错误。如何在没有构造函数的情况下修改此代码使其工作相同

我对编程不是很熟悉，所以我试着看看前面的问题。不知怎的，我想到了使用嵌套类（不知道它们是如何工作的），但没有用。该方法在它自己的类中时起作用

// Should be within a class

private PrintWriter _pw;

// This is the part that needs to go.
public HeapAlgo(PrintWriter pw) {
   this._pw = pw;
}

public void heapPermutation(String a[], int size, int n) throws IOException { 
// if size becomes 1 then prints the obtained 
// permutation 
    if (size == 1) 
        for (int i=0; i<n; i++) { 
            System.out.println(a[i] + "");
            this._pw.println(a[i] + ""); 
        }

    for (int i=0; i<size; i++) { 
        heapPermutation(a, size-1, n); 

        // if size is odd, swap first and last 
        // element 
        if (size % 2 == 1) { 
            String temp = a[0]; 
            a[0] = a[size-1]; 
            a[size-1] = temp; 
        }

        // If size is even, swap ith and last 
        // element 
        else { 
           String temp = a[i]; 
           a[i] = a[size-1]; 
           a[size-1] = temp; 
        } 
    }

}

public void heap() throws IOException 
{
FileWriter fw = new FileWriter("note.txt");
PrintWriter pw = new PrintWriter(fw);
File temp = new File("code.txt");
Scanner file = new Scanner(temp);

String substring = "";

    String a[] = new String[4];
  a[0] = "" + file.nextLine(); 
  a[1] = "" + file.nextLine();
  a[2] = "" + file.nextLine();
  a[3] = "" + file.nextLine();



HeapAlgo obj = new HeapAlgo(pw); // Pass in a writer
obj.heapPermutation(a, a.length, a.length);
pw.close();
} 

当我在一个大类中运行这些方法时，我得到一个错误\ “错误：无效的方法声明；需要返回类型”

任何帮助都将不胜感激。谢谢

编辑：我正在尝试编写此构造函数：

    public CodeRunner() 
    { 
    random(); 
    HeapAlgo.heap(//not sure if anything should go here); 
    algorithm(); 
    }

其中random（）创建随机字符串，algorithm函数对随机字符串的所有可能迭代执行算法。我试图为每组随机字符串创建对象

Answer 1

似乎以下元素应该位于名为HeapAlgo的类中：

1. 私有变量声明

private PrintWriter _pw;

1. 构造函数本身

public HeapAlgo(PrintWriter pw)

1. Heapper变异函数

public void heapPermutation(String a[], int size, int n) throws IOException

剩下的最后一个方法heap()应该放在另一个类中（可能在main()函数所在的位置）并从那里调用

或者，您确实可以使用内部类。将您提供的所有代码包装在一个类中（可能称为Heap），然后将上述三个元素包装在一个名为HeapAlgo的内部类中。类似这样的内容（我很快就把它打出来了，所以可能有错误需要修复）：

public class HeapUtil {
    public class HeapAlgo {
        private PrintWriter _pw;

        // This is the part that needs to go.
        public HeapAlgo(PrintWriter pw) {
           this._pw = pw;
        }

        public PrintWriter getPrintWriter(){
            return _pw;
        }

        public void heapPermutation(String a[], int size, int n) throws IOException { 
        // if size becomes 1 then prints the obtained 
        // permutation 
            if (size == 1) 
                for (int i=0; i<n; i++) { 
                    System.out.println(a[i] + "");
                    this._pw.println(a[i] + ""); 
                }

            for (int i=0; i<size; i++) { 
                heapPermutation(a, size-1, n); 

                // if size is odd, swap first and last 
                // element 
                if (size % 2 == 1) { 
                    String temp = a[0]; 
                    a[0] = a[size-1]; 
                    a[size-1] = temp; 
                }

                // If size is even, swap ith and last 
                // element 
                else { 
                   String temp = a[i]; 
                   a[i] = a[size-1]; 
                   a[size-1] = temp; 
                } 
            }
        }
    }

    public static HeapAlgo heap() throws IOException 
    {
        FileWriter fw = new FileWriter("note.txt");
        PrintWriter pw = new PrintWriter(fw);
        File temp = new File("code.txt");
        Scanner file = new Scanner(temp);

        String substring = "";

        String a[] = new String[4];
        a[0] = "" + file.nextLine(); 
        a[1] = "" + file.nextLine();
        a[2] = "" + file.nextLine();
        a[3] = "" + file.nextLine();

        HeapAlgo obj = new HeapAlgo(pw); // Pass in a writer
        obj.heapPermutation(a, a.length, a.length);
        return obj;
    }
}

请注意，在这种情况下，如果您希望在此类文件之外使用HeapAlgo，则需要使用Heap.HeapAlgo

---

编辑：尝试上面的代码（我编辑了它）。可能有一些错误，因为我没有实际运行它

用法如下：

public CodeRunner(){ 
    random(); 
    // heapAlgo is the heap object
    HeapAlgo heapAlgo = HeapUtil.heap(); 
    // this gives you access to the PrintWriter inside the HeapAlgo
    PrintWriter printWriter = heapAlgo.getPrintWriter();
    // do your other stuff
    algorithm(); 
}