public class Test {
  String s1;

  public Test(String s) {
    s1 = s;
  }

  public void m(String s) {
    s = s1;
  }

  public static void main(String[] args) {
    Test t = new Test("Bonjour");
    String s3 = "toto";
    t.m(s3);
    System.out.println(s3);
  }
}