String str = "23578075；677449,9865333qweeqweq;(陈)6789，sdfas ";
    Matcher m = Pattern.compile("[,，;；()（）](\\d{4})[,，;；()（）]").matcher(str);
    while(m.find())
      System.out.println(m.group(1));

------解决方案--------------------
用正则表达式应该很容易做到，下面是我的实验代码，请高手指教
Java code

import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class Test3 {
    public static void main(String[] args) {
        String str = "23578075；677449,9865333，qweeqweq;(陈)6789，sdfas 1234";
        String regex = "\\b\\d{4}\\b";
        Pattern p = Pattern.compile(regex);
        Matcher m = p.matcher(str);
        while(m.find()) {
            System.out.println(m.group());
        }
    }

}