SUN認證是給網路設計界建立的一套認證標準，Sun公司推出了Java以及Solaris技術認證方案。小編收集一些Sun java認證考試真題答案，希望髮夾認真做題!
1. What gets printed when the following program
is compiled and run?
class Test {
public static void main(String args[]) {
int i;
do {
i++;
} while (i < 0);
tln(i);
}
}
Select 1 correct answer:
A. The program does not compile as i is not initialized.
B. The program compiles but does not run.
C. The program compiles and runs but does not print anything.
D. The program prints 0.
E. The program prints 1.
答案：A：如果沒有初始化便使用基本變數型別，會導致編譯時異常，程式不能編譯。
2. What gets printed when the following program
is compiled and run?
public class XYZ {
public static void main(String args[]) {
int i,j,k;
for (i = 0; i < 3; i++)
{
for(j=1; j < 4; j++)
{
for(k=2; k<5; k++)
{
if((i == j) && (j==k))
tln(i);
} } } } }
Select 1 correct answer:
A. 0
B. 1
C. 2
D. 3
E. 4
答案：C
3. Given the following code :
class Base{}
public class MyCast extends Base{
static boolean b1=false;
static int i = -1;
static double d = 10.1;
public static void main(String argv[]){
MyCast m = new MyCast();
Base b = new Base();
//Here
}
}
Which of the following, if inserted at the comment //Here
will allow the code to compile and run without error?
Select 2 correct answers:
A. b = m;
B. m = b;
C. d = i;
D. b1 = i;
解析：A 從子型別到父型別的轉換是擴充套件引用轉換，不需要在執行時採取特殊的動作，不會在執行時丟擲異常。
B 從超型別到子型別的轉換是收縮引用轉換，需要在執行時執行測試，以查明實際的引用值是否是新型別的合法值.如果不是， 則會丟擲ClassCascException 。在這裡，b本身不是MyCast型別的值，因此會導致執行時異常。
C 從int到double的轉換是擴充套件基本轉換，基本型別之間的擴充套件轉換永遠不會導致執行時異常。但從int或long到float，或者是從long到double都可能導致精度丟失。
D 不允許進行int和boolean之間的型別轉換
答案：A、C
4. Given the following classes which of the following
will compile without error?
interface IFace{}
class CFace implements IFace{}
class Base{}
public class ObRef extends Base{
public static void main(String argv[])
{
ObRef ob = new ObRef();
Base b = new Base();
Object o1 = new Object();
IFace o2 = new CFace();
}
}
Select 3 correct answers:
A. o1 = o2;
B. b = ob;
C. ob = b;
D. o1 = b;
解析：A 任何物件都可以賦給Object型別的'物件，正確
B 子類賦給超類是擴充套件引用轉換，可以進行
C 收縮引用轉換，錯誤
D 擴充套件引用轉換，可以進行
答案 A B D
5. What is the result of compiling and running the following code?
1 public class Test {
2 static int total = 10;
3 public static void main (String args []) {
4 new Test();
5 }
6 public Test () {
7 tln("In test");
8 tln(this);
9 int temp = l;
10 if (temp > 5) {
11 tln(temp);
12 }
13 }
14 }
Select 1 correct answer:
A. The class will not compile
B. The compiler reports an error at line 2
C. The compiler reports an error at line 9
D. The value 10 is one of the printed elements
E. The class compiles but generates a runtime error
答案：D 由於test類沒有override toString方法，故在呼叫println(this)時會直接顯示類的有關資訊。
6. Carefully examine the following code:
public class StaticTest {
static { tln("Hi there"); }
public void print() {
tln("Hello");
}
public static void main(String args []) {
StaticTest st1 = new StaticTest();
t();
StaticTest st2 = new StaticTest();
t();
}}
When will the string "Hi there" be printed?
Select 1 correct answer:
A. Never
B. Each time a new instance is created
C. Once, when the class is first loaded into the JVM
D. Only when the static method is called explicitly
答案 C
Java虛擬機器規範約定，類的初始化發生在首次主動使用時。靜態變數和靜態初始化塊的先後，實際上取決於它們在類中出現的先後順序。
7. Given the following code what is the effect of a being 5?
public class Test {
public void add(int a) {
loop: for (int i = 1; i < 3; i++){
for (int j = 1; j < 3; j++) {
if (a == 5) {
break loop;
}
tln(i * j);
}
}
}
}
Select 1 correct answer:
A. Generates a runtime error
B. Throws an ArrayIndexOutOfBoundsException
C. Prints the values: 1, 2, 2, 4
D. Produces no output
解析：考察標記和break的使用。單純使用break只跳出當前迴圈(一層)。如果在要跳出的迴圈前加標記，那麼在加過標記的迴圈中的任何地方都可以使用break 標記 來跳出該迴圈
答案：D
