title: duplicate based on a set of values in a list
body: <p>I have a List of VO, need to find duplicate entries based on values? </p>
  
  <pre><code>name usageCount numberofReturns trendNumber nonTrendNumber trendType
  Name1   0           0              1           1             A
  Name2   0           0              1           1             B
  Name3   0           0              1           2             C
  Name4   0           0              2           2             D
  Name5   0           0              2           2             E
  </code></pre>
  
  <p>Current trend = "X"
  In this list i have to find out duplicate values using usagecount, numberofreturns, trendNumber and nonTrendnumber. Here (Name1 ,name 2) and (Name4,name5) are same, so i have to update the trendType value = X and leave Name 3 as it is.
  Is there any alternate way other then iterating the list with for loop and update the list value using CopyOnWriteArrayList(to avoid concurrent exception)?</p>