Java 递归方法打印次数过多？_Java_Recursion_Arraylist_Output

Java 递归方法打印次数过多？

java recursion

Java 递归方法打印次数过多？,java,recursion,arraylist,output,Java,Recursion,Arraylist,Output,所以我有一个方法，递归地对几何对象的数组进行排序，并按区域顺序打印出来。然而，我似乎无法解决这个小问题。我的方法是正确地打印数据，但它打印arraylist 6次而不是一次（它包含6个对象），知道我做错了什么吗？谢谢 private static void recursionSort(ArrayList<GeometricObject> list, int low, int high){ if (low < high){ int minIndex = l

所以我有一个方法，递归地对几何对象的数组进行排序，并按区域顺序打印出来。然而，我似乎无法解决这个小问题。我的方法是正确地打印数据，但它打印arraylist 6次而不是一次（它包含6个对象），知道我做错了什么吗？谢谢

private static void recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); //set min to first object in range
        for (int i = low + 1; i <= high; i++){ //loop through all values other than first
            if (list.get(i).getArea() < min.getArea()){ //check if the value is smaller than current min
                min = list.get(i); //if it is update the min
                minIndex = i; //store min index so we can swap locations later
            }
        }

        Collections.swap(list, low, minIndex); //move the original min to new min's old index (tricky wording)
        list.set(low, min); //set the old lowest to the new lowest using store min value

        recursionSort(list, low + 1, high); //call it again

    }
    System.out.println("Recursion sort:" + list);

}

我正在接收输出

Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]

您正在递归方法末尾打印列表。因为每次调用都会发生这种情况，所以一旦最内部的递归调用完成，每次递归调用都会打印列表

将“打印”移到递归方法之外的位置，使其刚好在进行初始递归调用之后。

这里的问题是，每个递归级别都会在返回之前打印出列表

要修复此问题，可以重载要打印的方法：

private static void recursionSort(ArrayList<GeometricObject> list){
    recursionSort(list, 0, list.size())
    System.out.println("Recursion sort:" + list);        
}

private static void recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); //set min to first object in range
        for (int i = low + 1; i <= high; i++){ //loop through all values other than first
            if (list.get(i).getArea() < min.getArea()){ //check if the value is smaller than current min
                min = list.get(i); //if it is update the min
                minIndex = i; //store min index so we can swap locations later
            }
        }

        Collections.swap(list, low, minIndex); //move the original min to new min's old index (tricky wording)
        list.set(low, min); //set the old lowest to the new lowest using store min value

        recursionSort(list, low + 1, high); //call it again

    }

}

私有静态无效递归排序（ArrayList列表）{
递归排序（list，0，list.size（））
System.out.println（“递归排序：+list”）；
}
私有静态void recursionSort（ArrayList list，int-low，int-high）{
如果（低<高）{
int minIndex=低；
GeometricObject min=list.get（低）；//将min设置为范围内的第一个对象
对于（int i=low+1；i您是否尝试从函数返回列表
public static void main (String args []){
    ArrayList<GeometricObject> list = new ArrayList<GeometricObject>();
    System.out.println(recursionSort(list, 0,list.size()-1).toString());
}

private static ArrayList<GeometricObject> recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); 
        for (int i = low + 1; i <= high; i++){ 
            if (list.get(i).getArea() < min.getArea()){ 
                min = list.get(i); 
                minIndex = i; 
            }
        }

        Collections.swap(list, low, minIndex);
        list.set(low, min);

        recursionSort(list, low + 1, high);

    }
    return list;

}   

publicstaticvoidmain（字符串参数[]）{
ArrayList=新建ArrayList（）；
System.out.println（递归排序（list，0，list.size（）-1.toString（））；
}
私有静态ArrayList recursionSort（ArrayList列表，整型低，整型高）{
如果（低<高）{
int minIndex=低；
GeometricObject min=list.get（低）；
对于（int i=low+1；i）你要递归6次，所以它要打印6次。在你的方法之外打印它。我尝试了上面的方法，但没有打印任何东西，我想我看到了这个想法，但是方法private static void recursionSort（ArrayList list）从未使用过，所以我仍然有点卡住。更改调用recursionSort的位置（list，low，high）
要使用recursionSort（list）相反，我只需将recursionSort（list，0，list.size（））更改为recursionSort（list，0，5），非常感谢！
public static void main (String args []){
    ArrayList<GeometricObject> list = new ArrayList<GeometricObject>();
    System.out.println(recursionSort(list, 0,list.size()-1).toString());
}

private static ArrayList<GeometricObject> recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); 
        for (int i = low + 1; i <= high; i++){ 
            if (list.get(i).getArea() < min.getArea()){ 
                min = list.get(i); 
                minIndex = i; 
            }
        }

        Collections.swap(list, low, minIndex);
        list.set(low, min);

        recursionSort(list, low + 1, high);

    }
    return list;

}