Java Programming Fundamentals

017 is an octal literal in Java, equal to decimal 15. The (byte) cast doesn't change the value since 15 fits in a byte. Right-shifting 15 (binary 1111) by 2 positions gives 3 (binary 11). Integer.toBinaryString(3) outputs '11'.

The compile-time type of myref is Question20, so its test() method throws Exception, requiring the try-catch (A is true). The runtime object is Question20Sub, so its test() executes, printing 'In Question20Sub' (C is true, B is false). Overriding methods aren't required to declare throws clauses (D is true, E is false).

obj[0]=new Object(), obj[1]=obj[-1] causes ArrayIndexOutOfBoundsException at i=1. However, re-examining: when i=1, i%2==0 is false, so obj[1]=obj[0]. Wait - obj[i-1] when i=1 is obj[0], which exists. So array fills: obj[0]=new Object(), obj[1]=obj[0] (same reference), obj[2]=obj[1] (same reference). All three entries point to one object. First if: obj[0]==obj[1] is true, assignment obj[1]=obj[2] is redundant but not null, prints '1'. Second if: obj[1]==obj[2] is true, obj[2]=obj[0] redundant, but && requires both sides - first part true so evaluation continues, prints '2'. Third if: obj[1]==obj[0] is true (short-circuit ||), skips assignment, prints '3'. Fourth if: | is non-short-circuit, so assignment executes but obj[0]==obj[2] always true, prints '4'. Final comparison: all three are same reference, so 'false false true'. Wait, re-tracing second if: after first if, obj[1]=obj[2] (same obj). obj[1]==obj[2] is true. && evaluates left to right, both conditions true. But re-reading the && logic more carefully - when obj[1]==obj[2] is true, it proceeds to check (obj[2]=obj[0])!=null. That's true. So '2' prints. Option C shows '1 2 4' - let me verify again. Actually looking at the answer C: '1 2 4 false false true'. The obj comparisons at end: obj[0]==obj[1] after all the shuffle... hmm.

Java is pass-by-value, but when you pass an object reference, you're passing the value of the reference (a pointer). This means the called method receives a reference to the same object, not a copy of the object. Changes to the object's state are visible to the caller.

Interface methods are implicitly public. When a class implements an interface, the implementing methods must be public. They cannot have weaker access (package-private or protected) because that would violate the interface contract.

Static methods must be invoked using the class name (ClassName.methodName()) or through an object reference (objectRef.methodName()), but never by method name alone. You need either the class context or an object reference to call a static method.

Static methods belong to the class rather than any specific instance. Therefore, they cannot directly access instance variables because those variables require a specific object instance to exist. They can only access other static members.

Methods can have the same name if they have different parameter lists (method overloading). The method signature includes the name AND parameter types, so multiple methods with the same name but different parameters are allowed in the same class.

In Java, 'length' is a public final field of an array object that stores the number of elements. Unlike Strings (which use length()) or Collections (which use size()), arrays use the '.length' property.

Option A is a valid declaration. Option C and D are valid initializations. Option B is invalid because you cannot specify the array dimension on the left side of the assignment in Java.

In Java, 'final' and 'static' are reserved keywords (all lowercase). 'Abstract' and 'Long' are not keywords; they are the capitalized names of a class or would be keywords only if lowercase ('abstract', 'long').

In Java, when a subclass object is created, the superclass constructor is called first (implicitly or explicitly). Therefore, A's constructor runs first, followed by B's constructor.

Class Mine extends abstract class MineBase but doesn't implement the abstract method amethod(). Therefore Mine must also be declared abstract. Concrete subclasses must implement all inherited abstract methods. The array initialization code is correct (Java arrays default to zero values), but the class declaration is the issue.

To solve this question, the user needs to understand the concept of substring and character indices.

The given code creates a string object s with value "Bicycle". The variables iBegin and iEnd have been assigned the values 1 and 3, respectively. The substring method is then called on the string object s with two arguments: iBegin and iEnd. The substring method extracts a portion of the string starting at the index specified by iBegin and ending at the index specified by iEnd-1.

Option A is incorrect because the substring method with arguments (1,3) extracts the portion of the string starting at index 1 and ending at index 2. Thus, the output is "Bi".

Option B is correct because the substring method with arguments (1,3) extracts the portion of the string starting at index 1 and ending at index 2. Thus, the output is "ic".

Option C is incorrect because the substring method with arguments (1,3) extracts the portion of the string starting at index 1 and ending at index 2. Thus, the output is "ic", not "icy".

Option D is incorrect because the syntax of the substring method is correct, and there is a matching method signature that takes an int and a char.

Therefore, the answer is:

The Answer is: B. ic

For inner classes (non-static nested classes), the modifiers public and private are legal at the class level within an outer class. However, 'static' is NOT legal for a non-static inner class - to make it static, it must be explicitly declared as a 'static nested class' with different syntax. The 'friend' keyword doesn't exist in Java.

To solve this question, the user needs to know the basics of Java programming language. The code creates an object of the Oct class and then calls the amethod() method, which initializes an integer variable oi with 012 and prints its value to the console.

In Java, leading zero in an integer literal denotes an octal (base-8) number. Therefore, the value 012 is an octal number that represents the decimal value 10.

So, the correct answer is:

The Answer is: C. 10