As you might knowJava does not support pointers, thus swapping things around could create problems.  In this post I will show an example of swapping two objects.

We have Employee class that holds information about Employees and SwapDemo3 class that will actually swap two employees inside a swap() method.

Swap() method will be using set and get methods of Employee class to get the private data from it.

So here is Employee Class we will be working with:

// an example on Java objects

// constructor
// instance variables, static variable
// methods: getters and setters
// keywords: this, new

public class Employee {

	public static int numberOfEmployees;

	private int   employeeID;
	private String employeeName;
	private String address;
	private String startingYear;

	public Employee( int id, String name, String addr, String year) {

		employeeID = id;
		employeeName = name;

		setAddress( addr );

		startingYear = year;

		numberOfEmployees++;
	}

	public Employee() { this(10000, null, null, null); };

//Set methods
	public void setAddress( String address ) {

		this.address = address;
	}

	public void setEmployeeID(int employeeID) {this.employeeID = employeeID;}
	public void setEmployeeName(String employeeName) {this.employeeName = employeeName;}
	public void setStartingYear(String startingYear) {this.startingYear = startingYear;}

//Get methods

	public String getAddress() { return address; }

	public int getEmployeeID() {return employeeID;}
	public String getEmployeeName() {return employeeName;}
	public String getStartingYear() {return startingYear;}

	public String toString() {

		String s;

		s =   "*****************************************n" +
		"         Employee Information        *n" +
		"*****************************************n" +
		"ID: " + employeeID + "n" +
		"Name: " + employeeName + "n" +
		"Address: " + address + "n" +
		"Starting Year: " + startingYear + "nn";

		return s;
	}

	public static void main( String args[] ) {

		Employee phil, george;

		phil = new Employee();
		System.out.println( phil );
		System.out.println( "t number of employees: " + Employee.numberOfEmployees +"n" );

// Part 2
		phil = new Employee( 10023, "Phil Coulthard",
			"70 The Pond, Seneca@York", "2002");

		george = new Employee( 10089, "George Farr",
			"678, IBM Toronto Lab", "1980" );

		System.out.println( phil );
		System.out.println( george );

		System.out.println( "t number of employees: " + Employee.numberOfEmployees );

// a special case about the default constructor:
// The Java compiler creates the default constructor if
// does not have *any* constructors
	}
}

and here is SwapDemo3 class that swaps 2 employees using get and set methods of the Employee class.

// A demo on pass-by-value in Java

public class SwapDemo3 {
	
	public void swap( Employee a, Employee b ) {
		
		int employeeId;
		String employeeName;
		String address;
		String startingYear;
		
		employeeId = a.getEmployeeID();
		a.setEmployeeID(b.getEmployeeID());
		b.setEmployeeID(employeeId);
		
		employeeName = a.getEmployeeName();
		a.setEmployeeName(b.getEmployeeName());
		b.setEmployeeName(employeeName);
		
		address = a.getAddress();
		a.setAddress(b.getAddress());
		b.setAddress(address);
		
		startingYear = a.getStartingYear();
		a.setStartingYear(b.getStartingYear());
		b.setStartingYear(startingYear);
		
	}
	
	public static void main(String[] args) {
		
		SwapDemo3 sd = new SwapDemo3();
		
		Employee one = new Employee( 12345, "John Doe", "70 The Pond", "1999" ),
		two = new Employee( 98765, "Mary Green", "45 King Street", "2007");
		
		System.out.println( one.toString() + two.toString() );
		
		System.out.println( "...swap swap swap" );
		
		sd.swap( one, two );
		
		System.out.println( "...back in main" );
		
		System.out.println( one );
		System.out.println( two );
	}
}

Program output is:

firstuser@firstuser:~/Desktop/JAC444/Week1$ java SwapDemo3
*****************************************
*           Employee Information        *
*****************************************
ID: 12345
Name: John Doe
Address: 70 The Pond
Starting Year: 1999

*****************************************
*           Employee Information        *
*****************************************
ID: 98765
Name: Mary Green
Address: 45 King Street
Starting Year: 2007

...swap swap swap
...back in main
*****************************************
*           Employee Information        *
*****************************************
ID: 98765
Name: Mary Green
Address: 45 King Street
Starting Year: 2007

*****************************************
*           Employee Information        *
*****************************************
ID: 12345
Name: John Doe
Address: 70 The Pond
Starting Year: 1999

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