Use this code numberOnly will contain your desired output.

   String str="sdfvsdf68fsdfsf8999fsdf09";
   String numberOnly= str.replaceAll("[^0-9]", "");

You may capture the value you need into a capturing group and access it with the corresponding code.

The regex for both Java and Python can look like

postgresql://[\d.]+:(\d+)\b

Details:

• postgresql:// - a literal string postgresql://
• [\d.]+ - 1 or more digits or . symbols
• : - a colon
• (\d+) - Group 1 capturing 1 or more digits
• \b - a word boundary.

See the Java demo:

String s = "Install: C:\\Program Files\\app\nDatabase: postgresql://127.0.0.1:42018/app\nStarted: 2016-12-28 10:40:05.908000\nLines: 1000000\nVersion: 4.1\nPID: 1736";
Pattern pattern = Pattern.compile("postgresql://[\\d.]+:(\\d+)\\b");
Matcher matcher = pattern.matcher(s);
if (matcher.find()){
    System.out.println(matcher.group(1)); 
} 

See the Python code:

import re
s = "Install: C:\\Program Files\\app\nDatabase: postgresql://127.0.0.1:42018/app\nStarted: 2016-12-28 10:40:05.908000\nLines: 1000000\nVersion: 4.1\nPID: 1736";
pattern = r"postgresql://[\d.]+:(\d+)\b"
m = re.search(pattern, s)
if m:
    print(m.group(1))

If your input string represents a Date then you could do

DateFormat df = new SimpleDateFormat("yyyyMMdd");
Date date = df.parse("19921231");

System.out.println(date.getMonth() + 1);

Or, you can also use the Calendar class as

Calendar cal = Calendar.getInstance();
cal.setTime(df.parse("19921231"));

System.out.println(cal.get(Calendar.DAY_OF_MONTH)); // 31
System.out.println(cal.get(Calendar.YEAR)); // 1992
System.out.println(cal.get(Calendar.MONTH) + 1); // 12