I found the definition about String:
String
in Oracle Jdk
extends Object
but Open Jdk
doesn't
And when i create an example code with generic type as:
public void testMethod(Map<String,?> map)
Map<String,String> tmpMap = new HashMap<String, String>();
tmpMap.put("Test", "Test");
testMethod(tmpMap);
it compile and run without any errors on two platforms.
? in Generic
is any types which extends from Object
So my question is:
See also:
The Java Language Specification says
The class
Object
is a superclass (§8.1.4) of all other classes.
So a class declared as
public class SomeType
is actually equivalent to
public class SomeType extends Object
So the String
class from your OpenJDK Java 7 link
public final class String implements java.io.Serializable, Comparable<String>, CharSequence
is actually equivalent to
public final class String extends Object implements java.io.Serializable, Comparable<String>, CharSequence
So that satisfies the Javadoc in the Oracle link.
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