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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Ideone
  6. {
  7. public static void main (String[] args) throws java.lang.Exception
  8. {
  9. String s = "abc 123 and 4";
  10. String res = s.replaceAll("\\D+", "");
  11. System.out.println(res);
  12. }
  13. }
Success #stdin #stdout 0.05s 4386816KB
stdin
Standard input is empty
stdout
1234