OnJava8-Examples/generics/UnboundedWildcards2.java

// generics/UnboundedWildcards2.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.*;

public class UnboundedWildcards2 {
  static Map map1;
  static Map<?,?> map2;
  static Map<String,?> map3;
  static void assign1(Map map) { map1 = map; }
  static void assign2(Map<?,?> map) { map2 = map; }
  static void assign3(Map<String,?> map) { map3 = map; }
  public static void main(String[] args) {
    assign1(new HashMap());
    assign2(new HashMap());
    //- assign3(new HashMap());
    // warning: [unchecked] unchecked method invocation:
    // method assign3 in class UnboundedWildcards2
    // is applied to given types
    //     assign3(new HashMap());
    //            ^
    //   required: Map<String,?>
    //   found: HashMap
    // warning: [unchecked] unchecked conversion
    //     assign3(new HashMap());
    //             ^
    //   required: Map<String,?>
    //   found:    HashMap
    // 2 warnings
    assign1(new HashMap<>());
    assign2(new HashMap<>());
    assign3(new HashMap<>());
  }
}