ArrayList sorting in Java

  1.ArrayList sequence from 36-digit number , randomly extracts 7 digits, where 7 digits cannot be duplicated, and sorts   public class Gty {public static void main (String [] args) {Random rd = new Random ();      　　　　　　　arraylist<integer> arr = new arraylist<integer> (); System.out.println (Math.random ()); while (true) {int temp = Rd.nextint (+1;if) (!arr.contains (temp)) {Arr.add (temp);}  if (Arr.size () ==7) {break;}}  Collections.sort (arr);   　　　　　　　　　　//in ascending order   //the first type: output mode  　　　　　　　　　　System.out.println (Arrays.tostring (Arr.toarray ()));  The second type: output mode//for (int i:arr) {//System.out.print (i+ ""); } collections.sort (Arr,collections.reverseorder ());  //in descending order  System.out.println (Arrays.tostring (Arr.toarray ()));} } 

2. The second method of sorting    
public class Gty {public static void main (string[] args) {arraylist<integer> arr = new arraylist<integer& gt; (); Arr.add (2); Arr.add (9); Arr.add (3); Arr.add (1); Arr.add (5); Arr.add (7); for (int i = 0; i < arr.size (); i++) {int min = i; Subscript for the smallest element for             (int j = i; J < Arr.size (), j + +) {if (arr.get (min) > Arr.get (j)) {min = j;}} int minValue = arr.get (min); Arr.set (Min,arr.get (i)); Arr.set (I,minvalue);} Set set = new HashSet (); HashSet will default to you sort for (int temp:arr) {set.add (temp); System.out.print (temp+ "  ");}}}

　　

　　

ArrayList sorting in Java