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400 Mock Questions on OCPJP 6 (formerly known as SCJP 1.6)
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Mock Exam - 2
Q1 import java.util.*;
public class Test1{
    public static void main(String a[]){
       Set s = new TreeSet();
       s.add(new Person(20));
       s.add(new Person(10));
       System.out.println(s);
    }
}
class Person{
   Person(int i){}
}
What is the output?
A1 10 20
A2 ClassCastException
A3 Compiler Error
A4 Compiler Error
Q2 import java.util.*;
public class Test2{
    public static void main(String a[]){
        Map s = new Hashtable();
        s.put(null,null);
        System.out.println(s);
    }
}
What is the output?

 

A1 [null = null]

 

A2 NullPointerException
A3 null
A4 []
Q3 import java.util.*;
public class Test3{
   public static void main(String a[]){
      Map s = new WeakHashMap(10);
      s.put(null,null);
      System.out.println(s);
   }
}

What is the output?
A1 [null = null]
A2 NullPointerException
A3 null
A4 []
Q4 import java.util.*;
public class Test4{
    public static void main(String a[]){
       Map s = new LinkedHashMap();
       s.put("1","one");
       s.put("3","three");
       s.put("2","two");
       System.out.println(s);
    }
}
What is the output?
A1 [1=one,3=three,2=two]
A2 NullPointerException
A3 [1=one,2=two,3=three]
A4 []
Q5 import java.util.*;
public class Test5{
    public static void main(String a[]){
       Map s = new HashMap();
       s.put("1","one");
       s.put("3","three");
       s.put("2","two");
       System.out.println(s);
    }
}
What is the output?
A1 [1=one,3=three,2=two]
A2 [3=three,2=two,1=one]
A3 cannot predict the order
A4 []
Q6 public class Test6{
    public static void method(float f){
       System.out.println("Float");
    }
    public static void method(double f){
       System.out.println("Double");
    }
    public static void main(String a[]){
       float f1 = 2.0f;
       float f2 = 2.0f;
       method(1.0);
       method(1.0f);
       method(1.0f*2.0f);
       method(1.0f*2.0);
       method(f1*f2);
    }
}

What is the output?

 
A1 Double Double Double Double Double
A2 Float Float Float Float Float
A3 Double Float Float Double Float
A4 Double Float Float Double Double
Q7 public class Test7{
   public static void method(byte b){
      System.out.println("Byte");
   }
   public static void method(int i){
      System.out.println("Int");
   }
   public static void main(String a[]){
      byte b = 1;
      method(1);
      method(128);
      method((byte)128);
      method(b);
   }
}
What is the output?
 
A1 Byte Int Int Byte
A2 Byte Int Int Byte
A3 Byte Int Byte Byte
A4 Int Int Byte Byte
Q8 public class Test8{
    public static void main(String a[]){
       byte b = 1;
       char c = 2;
       short s = 3;
       int i = 4;

       c = b; // 1
       s = b; // 2
       i = b; //3
       s = c * b; //4
    }
}
Which of the following are correct?
 
A1 Error at mark 1
A2 Error at mark 2
A3 Error at mark 3
A4 Error at mark 4
Q9 public class Test9{
public static void main(String a[]){
final byte b = 1;
char c = 2;
short s = 3;
int i = 4;

c = b; // 1
s = b; // 2
i = b; //3
s = c * b; //4
}
}
Which of the following are correct?

 

A1 Error at mark 1
A2 Error at mark 2
A3 Error at mark 3
A4 Error at mark 4
Q10 public class Test10{
     public static void main(String a[]){
        String s1 = "Sun";
        String s2 = "Java";
        s1.concat(s2);
        System.out.println(s1);
     }
}
What is output?

 

A1 Sun
A2 Java
A3 SunJava
A4 JavaSun
Q11 public class Test11{
    public static void main(String a[]){
       Integer i1 = new Integer(127);
       Integer i2 = new Integer(127);
       Long l = new Long(127);
       System.out.println(i1 == i2);
       System.out.println(i1.equals(i2));
       System.out.println(i1.equals(l));
    }
}
What is output?

 

A1 false true true
A2 true true true
A3 false true false
A4 Compiler Error
Q12 public class Test12{
   public static void main(String a[]){
       byte b = 100;
       Byte b1= new Byte(100);
       Byte b2 = new Byte(b);
       System.out.println(b1 == b2);
       System.out.println(b1.equals(b2));
   }
}

What is output?

 
A1 false true
A2 true false
A3 true true
A4 Compiler Error
Q13 public class Test13{
   public static void method(String s){
      System.out.println("String Version");
   }
   public static void method(StringBuffer sb){
      System.out.println("String Buffer Version");
   }
   public static void main(String a[]){
      method(null);
   }
}
What is output?

 

A1 String Version
A2 String Buffer Version
A3 Runtime Exception
A4 Compiler Error
Q14 public class Test14{
    static String s ="Instance";
    public static void method(String s){
        s+="Add";
    }
    public static void main(String a[]){
        Test14 t = new Test14();
        s = "New Instance";
        String s = "Local";
        method(s);
        System.out.println(s);
        System.out.println(t.s);
    }
}
What is output?

 

A1 Local Instance
A2 Local New Instance
A3 Loca Add New Instance
A4 Compiler Error
Q15 public class Test15{
    public static void method(StringBuffer sb){
        sb.append(" Added");
        sb = new StringBuffer("Hai");
    }
    public static void main(String a[]){
        StringBuffer sb = new StringBuffer("String Buffer");
        method(sb);
        System.out.println(sb);
    }
}
What is output?

 

A1 String Buffer
A2 String Buffer Added
A3 Hai
A4 Compiler Error
Q16 public class Test16{
    public static void method(StringBuffer sb){
        sb = new StringBuffer("Hai");
        sb.append(" Added");
    }
    public static void main(String a[]){
        StringBuffer sb = new StringBuffer("String Buffer");
        method(sb);
        System.out.println(sb);
    }
}
What is output?

 

A1 String Buffer
A2 String Buffer Added
A3 Hai
A4 Compiler Error
Q17 import java.util.*;
public class Test17{
    public static void main(String a[]){
        Map m = new Hashtable(10,0.75f);
        System.out.println(m.size());
    }
}
What is output?

 

A1  
A2 10
A3 7
A4 cOMPILER eRROR
Q18 What is the default capacity of java.util.Hashtable?
A1 10
A2 16
A3 11
A4 20
Q19 What is the default capacity of java.util.HashMap?
A1 10
A2 16
A3 11
A4 20
Q20 Which of the following classes has synchronized methods?
A1 ArrayList
A2 Vector
A3 HashTable
A4 WeakHashMap
Q21 public class Test21{
    public static void main(String a[]){
       String s1 = new String("Hai");
       String s2 = "Hai";
       String s3 = new String("Hai").intern();
       System.out.println(s1 == s2);
       System.out.println(s1 == s3);
       System.out.println(s2 == s3);
    }
}
What is output?
A1 false false true
A2 true false true
A3 false false false
A4 false true true
Q22 public class Test22{
    public static void main(String a[]){
       String s1 = "SunMicroSystems";
       System.out.println(s1.substring(0));
       System.out.println(s1.substring(1,4));
       System.out.println(s1.substring(8));
    }
}
What is output?

 

A1 SunMicrosystems sun oSystem
A2 SunMicrosystems unM Systems
A3 StringIndexOutOfBoundsException
A4 None Of the above
Q23 public class Test23{
    public static void main(String a[]){
        String s1 = "Sun";
        System.out.println(s1.substring(5));
    }
}
What is output?
A1 -1
A2 0
A3 StringIndexOutOfBoundsException
A4 ArrayIndexOutOfBoundsException
Q24 Which of the following are static methods in java.lang.String class?
A1 valueOf
A2 length
A3 indexOf
A4 All the above.
Q25 public class Test25{
   public static void main(String a[]){
      StringBuffer sb = new StringBuffer(8);
      sb.append("TestString");
      System.out.println(sb.capacity());
      System.out.println(sb.length());
   }
}

What is output?

 
A1 8 10
A2 10 10
A3 18 10
A4 18 18
Answers
1  ClassCastException
2 NullPointerException
3 [null = null]
4 [1=one,3=three,2=two]
5 cannot predict the order.
6 Double Float Float Double Float
7 Int Int Byte Byte
8 Error at mark 1
Error at mark 4
9 Error at mark 4
10 Sun
11 false true false
12 Compiler Error
13 Compiler Error
14 Local New Instance
15 String Buffer Added
16 String Buffer
17 0
18 11
19 16
20 Vector
HashTable
21 false false true
22 SunMicrosystems unM Systems
23 StringIndexOutOfBoundsException
24 valueOf
25 18 10
400 Mock Questions on OCPJP 6 (formerly known as SCJP 1.6)
JUST Rs.300 or 10 USD Send us mail to sales@javabeat.net more details
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