title: how to store date in particular format if input itself is a date?
body: <p>I am trying to store the expiry date in exp. The format I want to store it is "yyyy-MM-dd".I tried using SimpleDateFormat and than tried to format to get a string and than parse the string as follows:</p>
  
  <pre><code>SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  Date exp = sdf.parse(sdf.format(c.getTime()));
  </code></pre>
  
  <p>But result is I don't get date saved in exp as yyyy-MM-dd.
  I want to know given a date in particular format How do I convert it in other date format if the input itself is a date in one format and output is date is other format. I have used GregorianCalendar to getTime.</p>
  
  <p>The format of manufacturing date is"yyyy-MM-dd";
  I want the date to be stored in same format in exp;</p>
  
  <pre><code>public void calculateExpiryDate(List &lt;Item&gt; items) {
      Iterator &lt;Item&gt; itr = items.iterator();
  
      while (itr.hasNext()) {
          Item i = itr.next();
          Date md = i.getManufacturingDate();
          int ubm = i.getUseBeforeMonths();
  
          Calendar c = new GregorianCalendar();
          c.setTime(md);
          //System.out.println(c);
          c.add(Calendar.MONTH, ubm);
  
          Date exp = c.getTime();
          i.setExpiryDate(exp);
          SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
          System.out.println(md + " " + ubm + " " + sdf.format(exp) + "  " + " " + i.getId());
      }
  }
  </code></pre>
  
  <p>here is my code for Items:</p>
  
  <pre><code>public class Item implements Comparable&lt;Item&gt;{
      private int id;
      private String description;
      private float weight;
      private float price;
      private Date manufacturingDate;
      private int useBeforeMonths;
      private Date   expiryDate;
  
  
      public int getId() {
          return id;
      }
      public void setId(int id) {
          this.id = id;
      }
      public String getDescription() {
          return description;
      }
      public void setDescription(String description) {
          this.description = description;
      }
      public float getWeight() {
          return weight;
      }
      public void setWeight(float weight) {
          this.weight = weight;
      }
      public float getPrice() {
          return price;
      }
      public void setPrice(float price) {
          this.price = price;
      }
      public Date getManufacturingDate() {
          return manufacturingDate;
      }
      public void setManufacturingDate(Date manufacturingDate) {
          this.manufacturingDate = manufacturingDate;
      }
      public int getUseBeforeMonths() {
          return useBeforeMonths;
      }
      public void setUseBeforeMonths(int useBeforeMonths) {
          this.useBeforeMonths = useBeforeMonths;
      }
  
      public void setExpiryDate(Date expiryDate) {
          this.expiryDate = expiryDate;
      }
      public Date getExpiryDate() {
          return expiryDate;
      }
      @Override
      public int compareTo(Item arg0)
      {
          Date exp1=getExpiryDate();
          Date exp2=arg0.getExpiryDate();
          if(exp1.getYear()==exp2.getYear())
          {
              if(exp1.getMonth()==exp2.getMonth())
              {
                  return exp2.getDate()-exp1.getDate();
              }
              else
                  return exp2.getMonth()-exp1.getMonth();
          }
          return exp2.getYear()-exp1.getYear();
      }   
  
  } 
  </code></pre>