1.不带类型写法：

1	List listWithoutDup = new  ArrayList( new  HashSet(listWithDup));

2.带类型写法（以String类型为例）：

1) 7以下写法：

1	List<string> listWithoutDup = new  ArrayList<string>( new  HashSet<string>(listWithDup));</string></string></string>

2)Java 7及以上写法：

1	List<string> listWithoutDup = new  ArrayList<>( new  HashSet<>(listWithDup));</string>

样例：

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import  java.util.ArrayList; import  java.util.HashSet; import  java.util.List;   public  class  Test {      public  static  void  main(String[] args) {          List<string> listWithDup = new  ArrayList<string>();          listWithDup.add( "1" );          listWithDup.add( "2" );          listWithDup.add( "3" );          listWithDup.add( "1" );            List<string> listWithoutDup = new  ArrayList<string>( new  HashSet<string>(listWithDup));          System.out.println( "list with dup:" + listWithDup);          System.out.println( "list without dup:" + listWithoutDup);      } }</string></string></string></string></string>

样例运行结果： list with dup:[1, 2, 3, 1]

list without dup:[3, 2, 1]