Sun Java Certification Program
Fundamental classes
Questions 1 What is the output of the following:
StringBuffer sb1 = new StringBuffer("Amit");
StringBuffer sb2 = new StringBuffer("Amit");
String ss1 = "Amit";
System.out.println(sb1==sb2);
System.out.println(sb1.equals(sb2));
System.out.println(sb1.equals(ss1));
System.out.println("Poddar".substring(3));
a) false
false
false
dar
b) false
true
false
Poddar
c) Compiler Error
d) true
true
false
dar
Questions 2 Which of the following will output -4.0 ?
(a) System.out.println(Math.floor(-4.7));
(b) System.out.println(Math.round(-4.7));
(c) System.out.println(Math.ceil(-4.7));
(d) System.out.println(Math.min(-4.7));
Questions 3 What will be the result when you attempt to compile this program?
public class Rand {
public static void main(String argv[]){
int iRand;
iRand = Math.random();
System.out.println(iRand);
}
}
(a) Compile time error referring to a cast problem.
(b) A random number between 1 and 10.
(c) A random number between 0 and 1
(d) A compile time error about random being an unrecognised method.
Questions 4 What will be the result of compiling and running the given program?
Select one correct answer.
1 class Q2
2 {
3 public static void main(String arg[])
4 {
5 StringBuffer s[]={"A","B"};
6 System.out.println(s[0]+","+s[1]);
7 }
8 }
(a) Program compiles correctly and print A,B when executed.
(b) Compile time error.
(c) Run time error.
Questions 5 What will be the value of str after line no.7?
Enter your answer in the given field. Don't use any extra signs like ("")quotes or any string like "str=". For example, if your answer is the string "XYZ" you just write XYZ
1 class string
2 {
3 public static void main(String ds[])
4 {
5 String str="A";
6 str.concat("B");
7 str+="C";
8 }
9 }
Questions 6 What will be the result of compiling and running the given program?
Select one correct answer.
1 class strings
2 {
3 public static void main(String arg[])
4 {
5 if("String".indexOf("S",-10) ==0)
6 {
7 System.out.println("Equal");
8 }
9 else
10 {
11 System.out.println("Not Equal");
12 }
13 }
14 }
(a) Compile time error as we passed negative value in indexOf() method.
(b) Run time error as we passed negative value in indexOf() method.
(c) Program compiles and prints Equal when executed.
(d) Program compiles and prints Not Equal when executed.
Answers:1 (a)
No declaration is added, but When I run the example I found that the equals() method in the StringBuffer class is said that it is inherited from the Object class, and I think it didn’t override this method, as when I opened String class documentation it didn’t said that it inherits the equals() from the Object class, and it gave full description to it. And if this was true and the equals() method is the one inherited by the Object it is false, because it will return true only if the two reference denote the same object.
Answers:2 (c)
Options (a) and (b) will produce -5 and option 4 will not compile because the min method requires 2 parameters.
Answers:3 (a)
This is a bit of a sneaky one as the Math.random method returns a pseudo random number between 0 and 1, and thus option (c) is a plausible Answer. However the number returned is a double and so the compiler will complain that a cast is needed to convert a double to an int.
Answers:4 (b)
Compile time error:Casting needed to convert String to StringBuffer in line no. 5. [Mine opinion this will not work, to make it work new StringBuffer(“A”), new StringBuffer(“B”) ]
Answers:5) AC
After concatenating "B" in str the result is not stored so it will not effect at all.Moreover main reason behind this is that Strings are immutable,it always return new object which means if we don't save the results then it will not effect the orignal string at all.
Answers:6) (c)
We can use negative argument in indexOf() and lastIndexOf() method.In such case it will start searching from zero.
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