Re: What is wrong with my program?

SamuelXiao,
  Two SSCCEs, two code reviews, two rewrites.
I've learned a lot today. Thanks Lew. :)

import java.util.Arrays;

public class StudentFileReaderTest {

  public static void main(String[] args) {

    Integer[] students = new Integer[30];

    Integer[] file =
    {
        // Don't fill the heap unnecessarily
        Integer.valueOf(2),
        Integer.valueOf(3),
        Integer.valueOf(1),
        Integer.valueOf(2),
        Integer.valueOf(3)
    };

    int count = 0;

    if ( file.length > 0 )
    {
      for ( int ix = 0;
            // Watch your invariants
            ix < file.length && count < students.length;
            ++ix )
      {
        // Don't perform unnecessary iterations
        if( Arrays.binarySearch( students, 0, count, file [ix] ) < 0 )
        {
          students [count] = file[ix];
          // Don't be unnecessarily verbose
          Arrays.sort( students, 0, ++count );
        }
      }
    }

    for ( int ix = 0; ix < count; ++ix )
    {
      System.out.println( students [ix] );
    }

  }

}

Bo Vance started with this:

public class Scratch {

  static Integer[] students = new Integer[30];
  static int recordCount = 0;

  public static void main(String[] args) {

    Integer[] studentFile =
    {
        new Integer(2),
        new Integer(3),
        new Integer(1),
        new Integer(2),
        new Integer(3)
    };

    Arrays.fill(students, new Integer(-1));

    for (Integer studentRecord : studentFile) {
      addStudent(studentRecord);
    }

    recordCount = 0;
    Integer test = students[recordCount];
    while (test.intValue() < 0) {
      recordCount++;
      test = students[recordCount];
    }

    for (int i = recordCount; i < students.length; i++) {
      System.out.println(students[i]);
    }

  }

  static void addStudent(Integer student) {

    if(Arrays.binarySearch(students, student) < 0) {
      students[recordCount] = student;
      recordCount++;
    }
    Arrays.sort(students);
  }

}