Java. Find all numbers in the String.

Use RepalceAll

String str = "qwerty1qwerty2";      
str = str.replaceAll("[^0-9]+", " ");
System.out.println(Arrays.asList(str.trim().split(" ")));

Output:

[1, 2]

[EDIT]

If you want to include - a.e minus, add -?:

String str = "qwerty-1qwerty-2 455 f0gfg 4";      
str = str.replaceAll("[^-?0-9]+", " "); 
System.out.println(Arrays.asList(str.trim().split(" ")));

Output:

[-1, -2, 455, 0, 4]

Get number in indext:

 int k  = Integer.parseInt(Arrays.asList(str.trim().split(" ")).get(0));

OR

Pattern p = Pattern.compile("-?\\d+");
Matcher m = p.matcher("There are more than -2 and less than 12 numbers here");
while (m.find()) {
  System.out.println(m.group());
}

... prints -2 and 12.