[英]Is it possible to print out a Student object using RandomAccessFile?
[英]Need a way to write a Student from an ArrayList Store using RandomAccessFile
嘿我有問題。 我想使用一個arrayList來創建一個studentStore(我已經完成了這個),但是當我試圖用RandomAccessFile編寫學生時我一無所知。
StudentStore details = new StudentStore();
Student a = new Student("Becky O'Brien", "DKIT26", "0876126944", "bexo@hotmail.com");
Student b = new Student("Fabio Borini", "DKIT28", "0876136944", "fabioborini@gmail.com");
Student c = new Student("Gaston Ramirez", "DKIT29", "0419834501", "gramirez@webmail.com");
Student d = new Student("Luis Suarez", "DKIT7", "0868989878", "luissuarez@yahoo.com");
Student e = new Student("Andy Carroll", "DKIT9", "0853456788", "carroll123@hotmail.com");
這些是我的學生
現在我需要一種方法來寫它們
RandomAccessFile raf = new RandomAccessFile("employee.dat", "rw");
Student er = new Student(null, null, null, null);
for (int i = 0; i < details.length; i++) //This is getting an error obviously because details wont be taken. nor will a, b,c , d or e which is what the student was declared at the top.
{
er.setFirstName([i]);
er.setLastName(lnames[i]);
er.setAddress(addresses[i]);
er.setAge(ages[i]);
er.setSalary(salaries[i]);
er.write(raf);
}
raf = new RandomAccessFile("employee.dat", "rw");
er = new Student();
int numRecords = (int) raf.length() / er.size();
for (int i = 0; i < numRecords; i++) {
er.read(raf);
System.out.print(er.getStudentName() + " ");
System.out.print(er.getStudentId() + " ");
System.out.print(er.getStudentEmail() + " ");
System.out.print(er.getStudentTelephoneNumber() + " ");
}
raf.seek(0);
for (int i = 0; i < numRecords; i++) {
er.read(raf);
if (er.getAge() >= 55) {
er.setSalary(0.0);
raf.seek(raf.getFilePointer() - er.size());
er.write(raf);
raf.seek(raf.getFilePointer() - er.size());
er.read(raf);
}
System.out.print(er.getStudentName() + " ");
System.out.print(er.getStudentId() + " ");
System.out.print(er.getStudentEmail() + " ");
System.out.print(er.getStudentTelephoneNumber() + " ");
}
嘗試使用StudentStore
來獲取內部ArrayList
的大小。
public class StudentStore
{
ArrayList<Student> students = null;
public StudentStore()
{
students = new ArrayList<Student>();
}
public int size()
{
return (students == null) ? 0 : students.size();
}
}
但是,我不明白,為什么你必須創建自己的包裝ArrayList
而不是使用簡單的ArrayList
...
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