Vector is an object, which is passed by referencepublic static void main(String[] args){
Vector v=new Vector();
StringBuffer s=new StringBuffer("999");
v.addElement(s);
System.out.println((StringBuffer) v.firstElement()); //999
changeTest(v);
System.out.println((StringBuffer) v.firstElement()); /999-9999
}
public static void changeTest(Vector v){
Object o=v.firstElement();
if(o instanceof StringBuffer){
StringBuffer sb=(StringBuffer) o;
sb.append("-9999");
}
}
Vector v=new Vector();
StringBuffer s=new StringBuffer("999");
v.addElement(s);
System.out.println((StringBuffer) v.firstElement()); //999
changeTest(v);
System.out.println((StringBuffer) v.firstElement()); /999-9999
}
public static void changeTest(Vector v){
Object o=v.firstElement();
if(o instanceof StringBuffer){
StringBuffer sb=(StringBuffer) o;
sb.append("-9999");
}
}
import java.util.*;public class testvector {
public static void main(String[] args) {
System.out.println(getV().firstElement());
}
private static Vector getV(){
Vector a=new Vector();
String s="zkj"; a.addElement(s);
return a;
}
}