字符串答疑

public class TestString {
@Test
public void ch() {
String s1 = new String("amit");
String s2 = s1.replace('m', 'r');
String s3 = "arit";
System.out.println(s2 == s3);
}

public static void changeStr(String s) {
s = "welcome";
System.out.println(s);
}

public static void main(String[] args) {
String str = "abcd";
changeStr(str);
System.out.println(str);
}

}