Question

JAVA - Without using any built in functions implement a menu based program with the following array-based queue functions, ADD (at the end of array), INSERT (element at a given location), DELETE (element from a given location), SHOW (all array elements), COUNT (total number of elements), CLEAR (initialize array)

Answer 1

For this program, I've created a class to hold the array and it's methods (for better encapsulation). Refer to the comments to find the logic of each operation.  From what I've understood from the word clear, I've just reset it's length to 0. Hope it's right.

public class arrayProg {
public static void main(String args[]){
arr a = new arr();
a.add(10);
a.add(20);
a.show();
System.out.println();
a.add(30);
a.add(40);
a.show();
System.out.println();
a.insert(50,2);
a.show();
System.out.println();
a.delete(3);
a.show();
System.out.println();
System.out.println("Length of array is "+a.count());
a.clear();
a.show();
System.out.println();
}
}

class arr{
//length of the array
private int l;
//an empty array that holds all info
private int a[]=new int[100];
//add item at the end of the array
void add(int item){
a[l++]=item;
}
//insert item at position pos
void insert(int item,int pos){
if(pos>l){
//If position is not within length of the array
System.out.println("ERROR: Array not long enough");
return;
}
l++;
for(int j=l;j>pos;j--){
//move all elements after pos, one step ahead
a[j]=a[j-1];
}
a[pos]=item;
}
//delete element at given position
void delete(int pos){
if(pos>l){
//If position is not within length of the array
System.out.println("ERROR: Array not long enough");
return;
}
for(int j=pos;j<l;j++){
//move all element after pos, one position behind
a[j]=a[j+1];
}
l--;
}
//return number of elements
int count(){
return l;
}
//print the array
void show(){
if(l==0){
System.out.println("ERROR: Array empty!");
return;
}
for(int i=0;i<l;i++){
System.out.print(a[i]+" ");
}
}
//initialize array to 0s
void clear(){
l=0;
}
}

Here is the output:

10 20
10 20 30 40
10 20 50 30 40
10 20 50 40
Length of array is 4
ERROR: Array empty!