单项选择题

Which statement is true？（）……

Which statement is true？（）

A.The equals method does NOT properly override the Object.equals method.
B.Compilation fails because the private attribute p.name cannot be accessed in line 5.
C.To work correctly with hash-based data structures， this class must also implement the hashCode method.
D.When adding Person objects to a java.util.Set collection， the equals method in line 4 will prevent duplicates.

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单项选择题Which change can you make to Target without affecting Client？（）

A.Line 4 of class Target can be changed to return i++；
B.Line 2 of class Target can be changed to private int i = 1；
C.Line 3 of class Target can be changed to private int addOne（）{}；
D.Line 2 of class Target can be changed to private Integer i = 0；

单项选择题What is the result？（）

A.0
B.1
C.4
D.Compilation fails.
E.An exception is thrown at runtime.

多项选择题WhichtwoscenariosareNOTsafetoreplaceaStringBufferobjectwithaStringBuilderobject？（）

A.When using versions of Java technology earlier than 5.0.
B.When sharing a StringBuffer among multiple threads.
C.When using the java.io class StringBufferInputStream.
D.When you plan to reuse the StringBuffer to build more than one string.
E.Enitiation of separate design processes to the separation of users

单项选择题The variable df is an object of type DateFormat that has been initialized in line 11. What is the result if this code is run on December 14， 2000？（）

A.The value of s is 14-dic-2000.
B.The value of s is Dec 14， 2000.
C.An exception is thrown at runtime.
D.Compilation fails because of an error in line 13.

单项选择题What is the result？（）

A.int Long
B.Short Long
C.Compilation fails.
D.An exception is thrown at runtime.