Find the combination of any m numbers in a number of length n

The problem can be decomposed into:
1. First select the number with the largest number from n numbers, then select m-1 numbers from the remaining n-1 numbers, until n-(m-1) numbers are selected until 1 number is selected.
2. Select the next smallest number from n numbers and continue step 1 until the current number with the largest optional number is m.
Obviously, the above method is a recursive process, which means that all combinations can be obtained very cleanly using the recursive method.

Code:

package algorithm.ms100;
public class CtzHe {
private int[] array = {1,2,3,4,5};
private int[] b= new int[3];
private int M = 3;
public void combine( int a[], int n, int m)
{ 
for(int i=n; i>=m; i--)   // 注意这里的循环范围
{
 b[m-1] = i - 1;
 if (m > 1)
 combine(a,i-1,m-1);
 else                     // m == 1, 输出一个组合
 {   
 for(int j=M-1; j>=0; j--)
 System.out.print( a[b[j]] + " ");
 System.out.println();
 }
}
}
public static void main(String[] args) {
CtzHe c = new CtzHe();
c.combine(c.array, 5, 3);
}
}