OCJP(310-065)章节练习(2019.04.30)

单项选择题
Given:When line 14 is reached， how many objects are eligible for the garbage collector？（）
A.0
B.1
C.2
D.3
E.4
多项选择题
Given：Which two， inserted at line 11， will allow the code to compile？（）
A.public&ensp；class&ensp；MinMax<；？>；&ensp；{
B.public&ensp；class&ensp；MinMax<；？extends&ensp；Number>；&ensp；{
C.public&ensp；class&ensp；MinMax<；Nextends&ensp；Object>；&ensp；{
D.public&ensp；class&ensp；MinMax<；Nextends&ensp；Number>；&ensp；{
E.public&ensp；class&ensp；MinMax<；？extends&ensp；Object>；&ensp；{
F.public&ensp；class&ensp；MinMax<；Nextends&ensp；Integer>；&ensp；{
单项选择题
Given:What is the result when method testIfA is invoked？（）
A.True
B.Not true
C.An exception is thrown at runtime.
D.Compilation fails because of an error at line 12.
E.Compilation fails because of an error at line 19.
单项选择题
Which can appropriately be thrown by a programmer using Java SE technology to create a desktop application？（）
A.ClassCastException
B.NullPointerException
C.NoClassDefFoundError
D.NumberFormatException
E.ArrayIndexOutOfBoundsException
单项选择题
Given：Which statement is true about the class of an object that can reference the variable base？（）
A.It can be any class.
B.No class has access to base.
C.The class must belong to the geometry package.
D.The class must be a subclass of the class Hypotenuse.
多项选择题
A company has a business application that provides its users with many different reports：receivables reports， payables reports， revenue projects， and so on. The company has just purchased somenew， state-of-the-art， wireless printers， and a programmer has been assigned the task of enhancing all ofthe reports to use not only the company’s old printers， but the new wireless printers as well. When the programmer starts looking into the application， the programmer discovers that because of the design of theapplication， it is necessary to make changes to each report to support the new printers.Which two designconcepts most likely explain this situation？（）
A.Inheritance
B.Low cohesion
C.Tight coupling
D.High cohesion
E.Loose coupling
F.Object immutability
多项选择题
Given：Which two code fragments， inserted independently at line 13， will compile？（）
A.super（name， baseSalary）；
B.this.commission = commission；
C.super（）； this.commission = commission；
D.this.commission = commission； super（）；
E.super（name， baseSalary）； this.commission = commission；
单项选择题
Given：Which method will complete this class？（）
A.public int compareTo（Object o）{/*more code here*/}
B.public int compareTo（Score other）{/*more code here*/}
C.public int compare（Score s1，Score s2）{/*more code here*/}
D.public int compare（Object o1，Object o2）{/*more code here*/}
多项选择题
Which two scenarios are NOT safe to replace a StringBuffer object with a StringBuilder object？（）
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.
单项选择题
Given：foo and bar are public references available to many other threads. foo refers to a Thread and bar is anObject. The thread foo is currently executing bar.wait（）. From another thread，what provides the most reliable wayto ensure that foo will stop executing wait（）？
A.foo.notify（）；
B.bar.notify（）；
C.foo.notifyAll（）；
D.Thread.notify（）；
E.bar.notifyAll（）；