最新的Oracle 1Z0-851免費考試真題

問題1

Given:
1.import java.util.*;
2.public class WrappedString {
3.private String s;
4.public WrappedString(String s) { this.s = s; }
5.public static void main(String[] args) {
6.HashSet<Object> hs = new HashSet<Object>();
7.WrappedString ws1 = new WrappedString("aardvark");
8.WrappedString ws2 = new WrappedString("aardvark");
9.String s1 = new String("aardvark");
10.String s2 = new String("aardvark");
11.hs.add(ws1); hs.add(ws2); hs.add(s1); hs.add(s2);
12.System.out.println(hs.size()); } } What is the result?

A. 3

B. 4

C. 2

D. An exception is thrown at runtime.

E. 1

F. 0

G. Compilation fails.

正確答案: A

問題2

Given:
1.public class TestString3 {
2.public static void main(String[] args) {
3.// insert code here
5.System.out.println(s);
6.}
7.}
Which two code fragments, inserted independently at line 3, generate the output 4247? (Choose two.)

A. StringBuilder s = new StringBuilder("123456789");

B. delete(0,3).delete(1,3).delete(2,5).insert(1, "24");

C. StringBuffer s = new StringBuffer("123456789");

D. String s = "123456789"; s = (s-"123").replace(1,3,"24") - "89";

E. StringBuilder s = new StringBuilder("123456789");

F. delete(0,3).replace(1,3,"24").delete(4,6);

G. substring(3,6).delete(1,2).insert(1, "24");

H. substring(3,6).delete(1,3).insert(1, "24");

I. StringBuffer s = new StringBuffer("123456789");

正確答案: H,I

問題3

DRAG DROP
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正確答案:

問題4

Given:
11.public static void main(String[] args) {
12.Object obj = new int[] { 1, 2, 3 };
13.int[] someArray = (int[])obj;
14.for (int i : someArray) System.out.print(i + " ");
15.}
What is the result?

A. Compilation fails because of an error in line 12.

B. A ClassCastException is thrown at runtime.

C. 1 2 3

D. Compilation fails because of an error in line 13.

E. Compilation fails because of an error in line 14.

正確答案: C

問題5

Given:
11.public class Person {
12.private name;
13.public Person(String name) {
14.this.name = name;
15.}
16.public int hashCode() {
17.return 420;
18.}
19.}
Which statement is true?

A. Inserting a second Person object into a HashSet will cause the first Person object to be removed as a duplicate.

B. Deleting a Person key from a HashMap will delete all map entries for all keys of type Person.

C. The time to find the value from HashMap with a Person key depends on the size of the map.

D. The time to determine whether a Person object is contained in a HashSet is constant and does NOT depend on the size of the map.

正確答案: C

問題6

Given a pre-generics implementation of a method:
11.public static int sum(List list) {
12.int sum = 0;
13.for ( Iterator iter = list.iterator(); iter.hasNext(); ) {
14.int i = ((Integer)iter.next()).intValue();
15.sum += i;
16.}
17.return sum;
18.}
What three changes allow the class to be used with generics and avoid an unchecked warning? (Choose three.)

A. Replace the method declaration with "sum(List<Integer> intList)".

B. Replace line 13 with "for (int i : intList) {".

C. Replace line 14 with "int i = iter.next();".

D. Replace line 13 with "for (Iterator iter : intList) {".

E. Remove line 14.

F. Replace the method declaration with "sum(List<int> intList)".

正確答案: A,B,E

問題7

DRAG DROP
Click the Task button.

正確答案:

問題8

Given a pre-generics implementation of a method:
11.public static int sum(List list) {
12.int sum = 0;
13.for ( Iterator iter = list.iterator(); iter.hasNext(); ) {
14.int i = ((Integer)iter.next()).intValue();
15.sum += i;
16.}
17.return sum;
18.}
What three changes allow the class to be used with generics and avoid an unchecked warning? (Choose three.)

A. Replace the method declaration with "sum(List<Integer> intList)".

B. Replace line 13 with "for (int i : intList) {".

C. Replace line 14 with "int i = iter.next();".

D. Replace line 13 with "for (Iterator iter : intList) {".

E. Remove line 14.

F. Replace the method declaration with "sum(List<int> intList)".

正確答案: A,B,E

問題9

Given:
11.// insert code here
12.private N min, max;
13.public N getMin() { return min; }
14.public N getMax() { return max; }
15.public void add(N added) {
16.if (min == null || added.doubleValue() < min.doubleValue())
17.min = added;
18.if (max == null || added.doubleValue() > max.doubleValue()) 19. max = added;
20.}
21.}
Which two, inserted at line 11, will allow the code to compile? (Choose two.)

A. public class MinMax<?> {

B. public class MinMax<? extends Object> {

C. public class MinMax<N extends Number> {

D. public class MinMax<N extends Integer> {

E. public class MinMax<? extends Number> {

F. public class MinMax<N extends Object> {

正確答案: C,D

問題10

Given:
31.class Foo {
32.public int a = 3;
33.public void addFive() { a += 5; System.out.print("f "); }
34.}
35.class Bar extends Foo {
36.public int a = 8;
37.public void addFive() { this.a += 5; System.out.print("b " ); }
38.} Invoked with: Foo f = new Bar(); f.addFive(); System.out.println(f.a);
What is the result?

A. f 3

B. f 8

C. b 8

D. An exception is thrown at runtime.

E. f 13

F. b 3

G. Compilation fails.

H. b 13

正確答案: F

問題11

Given:
10.class One {
11.void foo() { }
12.}
13.class Two extends One {
14.//insert method here
15.}
Which three methods, inserted individually at line 14, will correctly complete class Two? (Choose three.)

A. int foo() { /* more code here */ }

B. private void foo() { /* more code here */ }

C. public void foo() { /* more code here */ }

D. void foo() { /* more code here */ }

E. protected void foo() { /* more code here */ }

正確答案: C,D,E

問題12

DRAG DROP
Click the Task button.

正確答案:

問題13

Given:
1.class Super {
2.private int a;
3.protected Super(int a) { this.a = a; }
4.} ...
11.class Sub extends Super {
12.public Sub(int a) { super(a); }
13.public Sub() { this.a = 5; }
14.}
Which two, independently, will allow Sub to compile? (Choose two.)

A. Change line 2 to: protected int a;

B. Change line 2 to: public int a;

C. Change line 13 to: public Sub() { super(a); }

D. Change line 13 to: public Sub() { this(5); }

E. Change line 13 to: public Sub() { super(5); }

正確答案: D,E

問題14

Given:
11.class Converter {
12.public static void main(String[] args) {
13.Integer i = args[0];
14.int j = 12;
15.System.out.println("It is " + (j==i) + " that j==i.");
16.}
17.}
What is the result when the programmer attempts to compile the code and run it with the command java Converter 12?

A. It is false that j==i.

B. An exception is thrown at runtime.

C. It is true that j==i.

D. Compilation fails because of an error in line 13.

正確答案: D

最新的Oracle Java Standard Edition 6 Programmer Certified Professional - 1Z0-851免費考試真題

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