transient Keyword

transient - keyword is used to declare instance variables that can't be saved, and shouldn't be transmitted as part of the view state for a Visualforce page (i.e. transient variables are not part of view state). 

Example 1 :
    Transient Integer currentTotal;

Example 2 : uing datetime variables

1. <apex:page controller="datetimecontroller" >
2. T1 : {!t1} - non transient - part of VF page viewstate - viewstate holds its value for after refresh use <br/>
3. T2 : {!t2} - transient - not part of VF page viewstate - gets new value from server for after refresh use <br/>
4. <apex:form >
5. <apex:commandLink value="refresh"/>
6. </apex:form>
7. </apex:page>

1. public with sharing class datetimecontroller {
2. datetime t1;
3. transient datetime t2;
4. public string getT2() {
5.     if (t2==null)
6.     t2=System.now();
7.     return ' '+t2;
8. }
9. public String getT1() {
10.     if(t1==null)
11.     t1=System.now();
12.     return ' '+t1;
13. }
14. }