菜鸟求教！！请问该JAVA代码如何写。

请问在输入完帐号密码打印("登录成功")后，在System.out.println("登录成功")后面加什么代码可以进入到public int system(Scanner sc) 这一步呢？求教！！
import java.util.Scanner;
public class StudentManager2{
private DataManager m;
public StudentManager2(){
m = new DataManager("E:\\javawork\\homework\\7\\data.txt");
m.load();//加载数据
}
public boolean login(Integer id,String password){
String[] strs = m.getAll();
for(int a=0;a<strs.length;a++){
String[] ip = strs[a].split(";");
if(ip[0].equals(id.toString())&&ip[1].equals(password))
return true;
}
return false;
}

public static void main(String[] args){
Scanner sc = new Scanner(System.in);
StudentManager sm = new StudentManager();
System.out.println("--------login--------");
System.out.println("please write admin id:");
int id = sc.nextInt();
System.out.println("please write password:");
String pwd = sc.next();
while(true){
if(sm.login(id,pwd)){
System.out.println("登录成功");
}else{
System.out.println("帐号密码不正确,谢谢使用");
break;
}
}
}
public int system(Scanner sc) {
System.out.println("-----------------------------");
System.out.println("1.查询全部学生信息");
System.out.println("2.查询指定学号的学生信息");
System.out.println("3.添加新的学生信息");
System.out.println("4.修改指定学号的学生信息");
System.out.println("5.删除指定学号的学生信息");
System.out.println("0.退出");
System.out.println("-----------------------------");
int index = sc.nextInt();
if (index < 0 && index > 5){
return -1;
}
return index;
} Student stu = new Student();
public void input(Scanner sc) {
System.out.print("请输入您的基本信息"); System.out.print("学号:");
long idNum = sc.nextLong(); System.out.print("姓名:");
String name = sc.next(); System.out.print("学院名称:");
String schoolName = sc.next(); System.out.print("系名称:");
String departmentName = sc.next(); System.out.print("班级编号:");
long classNum = sc.nextLong(); stu.setIdNum(idNum);
stu.setName(name);
stu.setSchoolName(schoolName);
stu.setDepartmentName(departmentName);
stu.setClassNum(classNum);
} public void showStudent(){
System.out.println(stu.goString());
}
}
class Student{
private long idNum;
private String name;
private String schoolName;
private String departmentName;
private long classNum;
public void setIdNum(long idNum){
this.idNum = idNum;
}
public long getIdNum(){
return idNum;
}
public void setName(String name){
this.name = name;
}
public String getName(){
return name;
}
public void setSchoolName(String schoolName){
this.schoolName = schoolName;
}
public String getSchoolName(){
return schoolName;
}
public void setDepartmentName(String departmentName){
this.departmentName = departmentName;
}
public String getDepartmentName(){
return departmentName;
}
public void setClassNum(long classNum) {
this.classNum = classNum;
}
public long getClassNum(){
return classNum;
}
public String goString(){
return "学号:"+this.idNum+" "+"姓名:"+this.name+" "+"学院名称:"+this.schoolName+" "+"系名称:"+this.departmentName+" "+"班级编号:"+this.classNum+" ";
}
}