Oracle 1Z0-851 問題集

質問 1：
DRAG DROP
Click the Task button.

正解：


質問 2：
A team of programmers is involved in reviewing a proposed design for a new utility class. After some discussion, they realize that the current design allows other classes to access methods in the utility class that should be accessible only to methods within the utility class itself. What design issue has the team discovered?
A. Tight coupling
B. High cohesion
C. Low cohesion
D. Strong encapsulation
E. Weak encapsulation
F. Loose coupling
正解：E

質問 3：
Given:
1.public class TestFive {
2.private int x;
3.public void foo() {
4.int current = x;
5.x = current + 1;
6.}
7.public void go() {
8.for(int i = 0; i < 5; i++) {
9.new Thread() {
10.public void run() {
11.foo();
12.System.out.print(x + ", ");
13.} }.start();
14.} }
Which two changes, taken together, would guarantee the output: 1, 2, 3, 4, 5, ? (Choose two.)
A. wrap the for loop code inside the go() method with a synchronized block synchronized(this) { // for loop code here }
B. change the variable declaration on line 2 to private volatile int x;
C. change line 7 to public synchronized void go() {
D. move the line 12 print statement into the foo() method
E. wrap the code inside the foo() method with a synchronized( this ) block
正解：D,E

質問 4：
Given:
23.Object [] myObjects = {
24.new Integer(12),
25.new String("foo"),
26.new Integer(5),
27.new Boolean(true)
28.};
29.Arrays.sort(myObjects);
30.for(int i=0; i<myObjects.length; i++) {
31.System.out.print(myObjects[i].toString());
32.System.out.print(" ");
33.}
What is the result?
A. The value of all four objects prints in natural order.
B. Compilation fails due to an error in line 29.
C. A ClassCastException occurs in line 31.
D. Compilation fails due to an error in line 23.
E. A ClassCastException occurs in line 29.
正解：E

質問 5：
Given:
10.class Nav{
11.public enum Direction { NORTH, SOUTH, EAST, WEST }
12.}
13.public class Sprite{
14.// insert code here
15.}
Which code, inserted at line 14, allows the Sprite class to compile?
A. Nav.Direction d = Nav.Direction.NORTH;
B. Direction d = NORTH;
C. Nav.Direction d = NORTH;
D. Direction d = Direction.NORTH;
正解：A

質問 6：
Given:
1.interface DoStuff2 {
2.float getRange(int low, int high); }
3.4.
interface DoMore {
5.float getAvg(int a, int b, int c); }
6.7.
abstract class DoAbstract implements DoStuff2, DoMore { }
8.9.
class DoStuff implements DoStuff2 {
10.public float getRange(int x, int y) { return 3.14f; } }
11.12.
interface DoAll extends DoMore {
13.float getAvg(int a, int b, int c, int d); } What is the result?
A. Compilation fails. Only lines 7 and 13 contain errors.
B. Compilation fails. Only line 12 contains an error.
C. Compilation fails. Only line 7 contains an error.
D. Compilation fails. Only line 13 contains an error.
E. Compilation fails. Only lines 7 and 12 contain errors.
F. The file will compile without error.
G. Compilation fails. Lines 7, 12, and 13 contain errors.
正解：F

質問 7：
Given:
1.public class GC {
2.private Object o;
3.private void doSomethingElse(Object obj) { o = obj; }
4.public void doSomething() {
5.Object o = new Object();
6.doSomethingElse(o);
7.o = new Object();
8.doSomethingElse(null);
9.o = null;
10.}
11.}
When the doSomething method is called, after which line does the Object created in line 5 become available for garbage collection?
A. Line 6
B. Line 10
C. Line 8
D. Line 5
E. Line 7
F. Line 9
正解：C

質問 8：
Given:
1.package com.company.application;
2.3.
public class MainClass {
4.public static void main(String[] args) {}
5.}
And MainClass exists in the /apps/com/company/application directory. Assume the CLASSPATH environment variable is set to "." (current directory). Which two java commands entered at the command line will run MainClass? (Choose two.)
A. java -classpath . MainClass if run from the /apps/com/company/application directory
B. java -classpath /apps/com/company/application:. MainClass if run from the /apps directory
C. java com.company.application.MainClass if run from the /apps/com/company/application directory
D. java MainClass if run from the /apps directory
E. java com.company.application.MainClass if run from the /apps directory
F. java -classpath /apps com.company.application.MainClass if run from any directory
正解：E,F