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试题1已知变量a和obj的定义如下：Object[] a1 = { “a”, “b”, “c” };Object obj = a1;则下面语句运行时会抛出异常的是( )。A. Object[] a2 = (Object[])obj;B. String str1 = (String)((Object[])obj)[1]C. String[] a3 = (String[])objD. String str2 = (String)a1[2] 试题2已知类Foo的定义如下：public class Foo {int value;Foo(int value) {this.value = value;}}运行下面程序段：Foo[] a1 = { new Foo(1), new Foo(2), new Foo(3) };Foo[] a2 = new Foo[a1.length];System.arraycopy(a1, 0, a2, 0, a1.length);System.out.println((a1 == a2) + “,” + (a1[1] == a2[1]));控制台输出的结果是( )。A. false,trueB. false,falseC. true,trueD. true,false 试题3已知类Foo的定义如下：public class Foo {int value;Foo(int value) {this.value = value;}public boolean equals(Object obj) {if (obj instanceof Foo) {Foo foo = (Foo) obj;return value == foo.value;} else {return false;}}运行下面程序段：ArrayList list = new ArrayList();HashSet set = new HashSet();list.add(new Foo(1));set.add(new Foo(1));System.out.println(list.contains(new Foo(1)) + “,”+ set.contains(new Foo(1)));控制台输出的结果是( )。 A.true,falseB. true,trueC. false,falseD. false,true 试题4已知类A、B、C和接口D的定义如下：public class A{…}public class B extends A implements D {…}public class C extends A {…}public interface D {…}变量a、b、c、d的定义如下：A a = new A(); B b = new B();C c = new C(); D d = null;则下列语句会有编译错误的是( )。 A. a = b;B. d = b;C. d = (D)a;D. c = (C)b; 试题5运行如下代码：class COne {public void f() {System.out.println(“COne.f”);}} class CTwo extends COne{public void f() {System.out.println(“CTwo.f”);}} class CThree {public void g(COne one) {System.out.println(“g(Cone)”);one.f();} public void g(CTwo two) {System.out.println(“g(Ctwo)”);two.f();}}public class Main {public static void main(String[] args) {COne one = new CTwo();CThree three = new CThree();three.g(one);}}控制台输出的结果是( )。 A. g(Cone)CTwo.fB. g(Cone)COne.fC. g(Ctwo)CTwo.fD. g(Ctwo)COne.f 试题6运行如下代码class Foo {private int value = 5;public Foo() {System.out.println(“Foo()”);System.out.println(value);}} class Bar extends F