Core Java Interview Questions On input and output, arrays, and strings.

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Core Java interview questions cover all the important questions of the topic mentioned above|Core Java Interview Questions On input and output, arrays, and strings|

These core Java interview questions are a great help to remember all the important highlights and important topics from each Java chapter|Core Java Interview Questions On input and output, arrays, and strings|

These interview questions will surely help to understand a few very confusing concepts in Java.

What is the difference between Systems dot out and system? err?

System. out and System. err both represent the monitor by default and hence can be used to send data or results to the monitor.

But system. out is used to display normal messages and results whereas system. err is used to display error messages.

On which memory, the array is created in Java?

Arrays are created on dynamic memory by JVM. There is no question of static memory in Java; everything (variable, array, object, etc.) is created on dynamic memory only.

Can you call the main method of a class from another class?

Yes, we can call the main () method of a class from another class using the class name. main().

At the time of calling the main() method, we should pass a string-type array to it.

Is string a class or data type?

The string is a class in ‘Java. lang’ package. But in Java, all classes are also considered data types. So we can take a string as a data type also

Can we call a class a data type?

Yes, a class is also called a user-defined data type. This is because a user can create a class.

What is object reference?

An object reference is a unique hexadecimal number representing the memory address of the object. It is useful to access the members of the object.

What is the difference between == and equal() while comparing strings? Which one is reliable?

== operator compares the references of the string objects, it does not compare the content of the objects.

the equal() method compares the contents. While comparing the strings, the equal() method should be used as it yields the correct result.

What is a string constant pool?

The string constant pool is a separate block of memory where the string objects are held by JVM.

If a string object is created directly, using the assignment operator as string s1 = “hello”, then it is stored in the string constant pool.

Explain the difference between the following statements.

String s = “Hello”;
String s = new String(“Hello”);

In the first statement, the assignment operator is used to assign the string literal to the string variable s.

In this case, JVM first checks whether the same object is already available in the string constant pool.

If it is available, then it creates another reference for it. If the same object is not available, then it creates another object with the content “Hello” and stores it in the string constant pool.

In the second statement, a new operator is used to create the string object. In this case, JVM always creates a new object without looking in the string constant pool.

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