quy doi 24h

public String test(String fulltime){
    // Kiem tra xem string time co ky tu : phan cach hay khong
    if(fulltime.indexOf(":")==-1)
    {
        throw new IllegalArgumentException("Khong hop le");
    }

    // Chia ra 2 strings - Trong do time[0] la gio, time[1] la phut
    String[] time = fulltime.split(":");

    // Kiem tra length cua 2 chuoi xem co hop le hay khong
    if(time[0].length() > 2 || time[0].length() < 1)
    {
        throw new IllegalArgumentException("Gio khong hop le");
    }
    if(time[1].length() > 2 || time[1].length() < 1)
    {
        throw new IllegalArgumentException("Phut khong hop le");
    }

    // Kiem tra gia tri gio co hop le hay khong (0-24)
    if(time[0].length()==1)
    {
        if(time[0].charAt(0) < '0' || time[0].charAt(0) > '9')
        {
          throw new IllegalArgumentException("Gio khong hop le");
        }
    }else{
        // Neu length la 2 ky tu thi kiem tra xem co hop le hay khong
        // Kiem tra ky tu dau tien (phai la 0->2 vi toi da la 24h)
        if(time[0].charAt(0) < '0' || time[0].charAt(0) > '2' )
        {
          throw new IllegalArgumentException("Gio khong hop le");
        }
        // Kiem tra ky tu thu 2 (0->9)
        if(time[0].charAt(1) < '0' || time[0].charAt(1) > '9')
        {
          throw new IllegalArgumentException("Gio khong hop le");
        }
    }
    if(Integer.parseInt(time[0]) > 23){
        throw new IllegalArgumentException("Gio khong hop le");
    }

    // Kiem tra gia tri phut co hop le hay khong
    if(time[1].length()==1)
    {
        if(time[1].charAt(0) < '0' || time[1].charAt(0) > '9')
        {
          throw new IllegalArgumentException("Gio khong hop le");
        }
        // Them so 0 vao dau neu chi dien 1 ky tu
        time[1] = "0"+time[1];
    }else{
        // Neu length la 2 ky tu thi kiem tra xem co hop le hay khong
        // Kiem tra ky tu dau tien (phai la 0->6 vi toi da la 60 phut)
        if(time[1].charAt(0) < '0' || time[1].charAt(0) > '6' )
        {
          throw new IllegalArgumentException("Phut khong hop le");
        }
        // Kiem tra ky tu thu 2 (0->9)
        if(time[1].charAt(1) < '0' || time[1].charAt(1) > '9')
        {
          throw new IllegalArgumentException("Phut khong hop le");
        }
    }
    if(Integer.parseInt(time[1]) > 59){
        throw new IllegalArgumentException("Phut khong hop le");
    }

    // Quy doi gio
    if(Integer.parseInt(time[0]) == 0 )
    {
        return "12:"+time[1]+"am";
    }else if(Integer.parseInt(time[0]) > 11 ){
        int hour = Integer.parseInt(time[0])-12;
        if(hour > 0)
        {
            return hour+":"+time[1]+"pm";
        }else{
            return time[0]+":"+time[1]+"pm";
        }
    }else{
        return time[0]+":"+time[1]+"am";
    }
  }