Deepak Surya

There are 8 primitive data types Turn back

String class is also a data type. It is immutable.

Scanner class is used to read input.

An array is a reference data type, meaning that it's just an address

Functions declared static don't need the creation of an instance for being accessed or used.

Object is a superclass of everything we create in java

A subclass can be generalized to a superclass. A superclass cannot become a more specific subclass.

If a superclass does not have a default constructor(constructor without parameters), any subclasses extending it must make an explicit call to one of the parameterized constructors of the superclass.

An abstract method is a method declared without an implementation. Abstract methods don't have a body. Abstract classes may have abstract and non-abstract methods.

Classes being written in the same file should not have access modifiers or the code will not execute.

Miss data arguments in printf while trying to print the value of something, We get a warning saying that there are more '%' conversions than data arguments

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Heap's algorithm generates all possible permutations of n objects.

It generates each permutation from the previous one by interchanging a single pair of elements; the other n-2 elements are not disturbed

First set a counter i to 0. Now we perform the following steps repeatedly until i is equal to n.

We use the algorithm to generate the (n-1)! permutations of the first n-1 elements, adjoining the last element to each of these.

Thus we generate all of the permutations that end with the last element.

Then if n is odd, we switch the first element and the last one.

If n is even, we switch the i-th element with the last one.

Note that there's no difference between n even and n odd in the first iteration.

Now we add one to the counter i and repeat.

In each iteration, the algorithm will produce all of the permutations that end with the element that has just been moved to the "last" position.