title: How to replace authors names with unique numbers in java using hashmap
body: <p>I have a CSV file which is a coauthorship network.Entries are like this:</p>
  
  <pre><code>1992,M_DINE,R_LEIGH,P_HUET,A_LINDE,D_LINDE
  
  1992,C_BURGESS,J_CLINE,M_LUTY
  
  1992,M_DINE,R_LEIGH,P_HUET,A_LINDE,D_LINDE
  
  1992,F_ZWIRNER
  
  1992,O_HERNANDEZ
  ...
  </code></pre>
  
  <p>I want to replace all the authors names with unique numbers using hashmaps
  I want the output to be sth like this:</p>
  
  <pre><code>    M_DINE   1
  
      R_LEIGH  2
  
      P_HUET   3
  
      ...
  </code></pre>
  
  <p>and I do not want the years to be included.</p>