Intro to Java Programming Can you explain or comment on what happens in the code

Question

Intro to Java Programming

Can you explain or comment on what happens in the code below, step-by-step?

public class InvItem {

private static int curID = 1;

private int id;

private String loc;

public InvItem() {

id = -1;

loc = "";

}
public InvItem(String loc) {

this.id = curID;

this.loc = loc;

curID++;

}
public int getId() { return id; }
public String getLoc() { return loc; }
public void setLoc(String loc) { this.loc = loc;}

public static void main(String[] args){

InvItem[] items = new InvItem[4];
items[0] = new InvItem("B1");

items[1] = new InvItem("FRONT");

items[2] = new InvItem("SHIPPING");

items[3] = items[2];

items[2].setLoc("QC HOLD");

System.out.println("Item ID: " + items[0].getId() + " Items Location: " + items[0].getLoc()); System.out.println("Item ID: " + items[1].getId() + " Items Location: " + items[1].getLoc()); System.out.println("Item ID: " + items[2].getId() + " Items Location: " + items[2].getLoc()); System.out.println("Item ID: " + items[3].getId() + " Items Location: " + items[3].getLoc());
}
}

Explanation / Answer

/*
Java Class InvItem
This Java class InvItem describes how class is defined and being used
in Java language.

Syntax of defining java class is,
<modifier> class <class-name>{
// members and methods
}
*/

public class InvItem {
/*
Syntax of defining memebers of the java class is,
<modifier> type <name>;
   here InvItem is class name
*/
private static int curID = 1;/*
Syntax of defining memebers of the java class is,
<modifier> type <name>;
*/
private int id;//here private is modifier int is datatype and id is name of memeber/variable of class
private String loc;//here private is modifier String is datatype and loc is name of memeber of class
public InvItem()
{
id = -1;//id is variable or data member whose value is -1
loc = "";
}
public InvItem(String loc) {
this.id = curID;// this keyword represent current instance of class.
this.loc = loc;/*The this() constructor call should be used to reuse the constructor in the constructor.
It maintains the chain between the constructors i.e. it is used for constructor chaining. */
curID++;
/*

       * Java increment operator ++ increases its operand's value by one
* while decrement operator -- decreases its operand's value by
* one as given below.
*/
}
/*
Syntax of defining methods of the java class is,
<modifier> <return-type> methodName(<optional-parameter-list>) <exception-list>{
...
}
*/
public int getId()
{
return id;/return the id
}
public String getLoc() { return loc; }
public void setLoc(String loc)
//set passed parameter as name
{ this.loc = loc;}
public static void main(String[] args) //main method will be called first when program is executed
{
/*
Syntax of java object creation is,
<class-name> object-name = new <class-constructor>;

*/
InvItem[] items = new InvItem[4];
items[0] = new InvItem("B1");
items[1] = new InvItem("FRONT");
items[2] = new InvItem("SHIPPING");
items[3] = items[2];
items[2].setLoc("QC HOLD");
// It will print the value of Item ID,ItemLocation according to the array value
System.out.println("Item ID: " + items[0].getId() + " Items Location: " + items[0].getLoc()); //will print Item ID: 1 Items Location: B1
System.out.println("Item ID: " + items[1].getId() + " Items Location: " + items[1].getLoc());//will print Item ID: 2 Items Location: FRONT
System.out.println("Item ID: " + items[2].getId() + " Items Location: " + items[2].getLoc()); //will print Item ID: 3 Items Location: QC HOLD
System.out.println("Item ID: " + items[3].getId() + " Items Location: " + items[3].getLoc());//will print Item ID: 3 Items Location: QC HOLD
}
}

output:
Item ID: 1 Items Location: B1
Item ID: 2 Items Location: FRONT
Item ID: 3 Items Location: QC HOLD
Item ID: 3 Items Location: QC HOLD

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