[Java] 在Java 8中将List转换为Map对象方法

<b>public</b> <b>class</b> employee {
  <font><i>// member variables</i></font><font>
  <b>private</b> <b>int</b> empid;
  <b>private</b> string empname;
  <b>private</b> <b>int</b> empage;
  <b>private</b> string empdesignation;
</font>

<font><i>// convert list<employee> to map<empid, empname> using java 8 streams</i></font><font>
 map<integer, string> mapofemployees = employees.stream().collect(
  collectors.tomap(e -> e.getempid(),e -> e.getempname()));
</font>

<font><i>// convert list<employee> to map<empid, empname> using java 8 streams</i></font><font>
map<integer, employee> mapofemployees = employees.stream().collect(
    collectors.tomap( e -> e.getempid(), e -> e));
</font>

map<integer, string> mapofemployees = employees.stream().collect(
    collectors.tomap(
      e -> e.getempid(), 
      e -> e.getempname(), 
      (e1, e2) -> e1 )); <font><i>// merge function</i></font><font>
</font>

map<integer, string> mapofemployees = employees.stream().collect(
    collectors.tomap(
      e -> e.getempid(), 
      e -> e.getempname(), 
      (e1, e2) -> e1 , <font><i>// merge function</i></font><font>
      treemap<integer, string>::<b>new</b>)); </font><font><i>// map supplier</i></font><font>
</font>

() -> new treemap<integer, string>(new mycomparator())