我正在编写一个程序，该程序应该输出一个数组，该数组的元素反转，该数组的和，该数组的平均值，该数组的最小值和最大值以及该数组进行排序（按选择排序的升序和降序排列）按气泡排序）。一切似乎都已检出，但模块descendingOrderBBS（）的输出不正确。到目前为止，这是我的代码：
import java.util.Scanner;
import java.lang.String;
public class Main
{
public static String input;
public static int n;
public static void main(String[] args)
{
int[] file1 = new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int[] file2 = new int[]{2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
int[] file3 = new int[]{1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21};
inputData();
switch (input)
{
case "file1":
{
System.out.println("original array: ");
printArray(file1);
System.out.println(" ");
System.out.println("reversed array: ");
reverseArray(file1);
System.out.println(" ");
System.out.println("The sum of all elements: " + sum(file1));
System.out.printf("The average of all elements: %.1f%n", average(file1));
max(file1);
min(file1);
//System.out.printf("Array in ascending order (Selection Sort): %-10s", ascendingOrderSS(file1));
ascendingOrderSS(file1);
System.out.println(" ");
descendingOrderBBS(file1);
//System.out.printf("Array in ascending order (Bubble Sort): %-10s", ascendingOrder(file1));
break;
}
case "file2":
{
System.out.println(file2);
break;
}
case "file3":
{
System.out.println(file3);
break;
}
default :
{
Scanner keyboard = new Scanner(System.in);
System.out.println("File not found, try again: ");
inputData();
break;
}
}
}
private static String inputData()
{
Scanner keyboard = new Scanner(System.in);
System.out.print("Please input file: ");
input = keyboard.nextLine();
return input;
}
private static void printArray(int f[])
{
for (int i = 0; i < f.length; i++)
{
System.out.printf("%-10s", f[i]);
}
}
private static void reverseArray(int f[])
{
int end = f.length - 1;
for (int start = 0; start < end; start++, end--)
{
int temp = f[start];
f[start] = f[end];
f[end] = temp;
}
for (int i = 0; i < f.length; i++)
{
System.out.printf("%-10s", f[i]);
}
}
private static int sum(int f[])
{
int sum = 0;
for (int i = 0; i < f.length; i++)
{
sum += f[i];
}
return sum;
}
private static float average(int f[])
{
float average = 0;
int sum = 0;
for (int i = 0; i < f.length; i++)
{
sum += f[i];
}
average = sum / f.length;
return average;
}
private static void max(int f[])
{
int largest = f[0];
for (int i = 0; i < f.length; i++)
{
if (f[i] > largest)
{
largest = f[i];
}
}
System.out.println("Max: " + largest);
}
private static void min(int f[])
{
int smallest = f[0];
for (int i = 0; i < f.length; i++)
{
if (f[i] < smallest)
{
smallest = f[i];
}
}
System.out.println("Min: " + smallest);
}
private static void descendingOrderBBS(int f [])
{
int i = 0;
int j = 0;
int temp = 0;
for (i = 0; i < f.length; i++)
{
for (j = i + 1; j < f.length; j++)
if (f[i] < f[j])
{
temp = f[i];
f[i] = f[j];
f[j] = temp;
}
}
System.out.println("Array in descending order (Bubble Sort): ");
for (int x = 0; x < f.length; x++)
{
System.out.printf("%-10s", f[x]);
}
}
private static void ascendingOrderSS( int f [])
{
int a = 0;
int b = 0;
int minIndex = 0;
for (a = 0; a < f.length - 1; a++)
{
minIndex = a;
for (b = a + 1; b < f.length; b++)
{
if (f[b] < f[minIndex])
{
minIndex = b;
}
}
int temp = f[minIndex];
f[minIndex] = f[a];
f[a] = temp;
}
System.out.println("Array in ascending order (Selection Sort): ");
for (int x = 0; x < f.length; x++)
{
System.out.printf("%-10s", f[x]);
}
}
}
这是整个程序一起运行
Please input file: file1
original array:
1 2 3 4 5 6 7 8 9 10
reversed array:
10 9 8 7 6 5 4 3 2 1
The sum of all elements: 55
The average of all elements: 5.0
Max: 10
Min: 1
Array in ascending order (Selection Sort):
1 2 3 4 5 6 7 8 9 10
Array in descending order (Bubble Sort):
2 1 3 4 5 6 7 8 9 10
Process finished with exit code 0
我尝试将变量更改为a / b而不是i / j。我将所有模块设为私有，以查看这是否有所作为，但是我尝试过的任何事情都没有做。哦，我也尝试使用不同的IDE。 这是两个排序模块一起的输出：
ascendingOrderSS(file1);
System.out.println(" ");
descendingOrderBBS(file1);
Array in ascending order (Selection Sort):
1 2 3 4 5 6 7 8 9 10
Array in descending order (Bubble Sort):
2 1 3 4 5 6 7 8 9 10
Process finished with exit code 0
忽略升序模块的输出：
//ascendingOrderSS(file1);
System.out.println(" ");
descendingOrderBBS(file1);
Array in descending order (Bubble Sort):
10 9 8 7 6 5 4 3 2 1
Process finished with exit code 0
我不确定为什么DescendingOrderBBS（）正在更改。我已经完成了最后一个项目，直到凌晨5:12。
所有固定：
Array in ascending order (Selection Sort):
1 2 3 4 5 6 7 8 9 10
Array in descending order (Bubble Sort):
10 9 8 7 6 5 4 3 2 1
Process finished with exit code 0
答案 0 :(得分：1)
对于您的第一个问题，为什么打印5.0而不打印5.5是因为sum / f.length是整数的除法，并且.之后的值将被删除，但是转向将sum植入float或将sum投射到float将解决此问题。
您当前的代码（显示1.0）
float average = 3 / 2;
System.out.println(average);
修复程序（此打印为1.5）：
float sum = (float)3 / 2;
System.out.println(sum);
3和2是代码中的变量sum和f.length。