List and ArrayList Example: Hi friends this is my first post on core java. I think you know the basics of Collections. I am not explaining basics here. When i am learning java I saw so many sites are giving examples only on Collections to add integer or string or float. Little bit sites only giving example on adding objects and retrieving then from Collections. this is my first example using java.util.List and java.util.Arraylist. i am not explaining anything about this example.I think you can understand by seeing this example.
the usage of this example is understanding List and ArrayList and contains method. we are adding employee to a list and avoiding duplicates while adding to list by overriding equals method. and retrieving all employees and displaying them from List. have any questions contact me or post a comment below.
Employee.java;
package com.jagadeesh.domain;
public interface Employee {
public Integer getId();
public void setId(Integer id);
public String getFirstName();
public void setFirstName(String firstName);
public String getLastName();
public void setLastName(String lastName);
public void setEmail(String email);
public String getEmail();
public int getPriority();
public void setPriority(int priority);
public String getDesignation();
public void setDesignation(String designation);
public String toDisplayString();
}
EmployeeImpl.java
package com.jagadeesh.domain.impl;
import java.io.Serializable;
import com.jagadeesh.domain.Employee;
import com.jagadeesh.utils.EmployeeIO;
public class EmployeeImpl extends EmployeeIO
implements Employee {
private static final long serialVersionUID = 5058287999709032283L;
private Integer id;
private String firstName;
private String lastName;
private String email;
private int priority;
private String designation;
@Override
public Integer getId() {
return id;
}
@Override
public void setId(Integer id) {
this.id = id;
}
@Override
public String getFirstName() {
return firstName;
}
@Override
public void setFirstName(String firstName) {
this.firstName = firstName;
}
@Override
public String getLastName() {
return lastName;
}
@Override
public void setLastName(String lastName) {
this.lastName = lastName;
}
@Override
public String getEmail() {
return email;
}
@Override
public void setEmail(String email) {
this.email = email;
}
@Override
public int getPriority() {
return priority;
}
@Override
public void setPriority(int priority) {
this.priority = priority;
}
@Override
public String getDesignation() {
return designation;
}
@Override
public void setDesignation(String designation) {
if ("CEO".equalsIgnoreCase(designation)) {
setPriority(1);
} else if ("MD".equalsIgnoreCase(designation)) {
setPriority(2);
} else if ("HR".equalsIgnoreCase(designation)) {
setPriority(3);
} else {
setPriority(4);
}
this.designation = designation;
}
@Override
public String toString() {
StringBuffer buffer = new StringBuffer();
buffer.append("EmployeeImpl [id=");
buffer.append(id);
buffer.append(", firstName=");
buffer.append(firstName);
buffer.append(", lastName=");
buffer.append(lastName);
buffer.append(", email=");
buffer.append(email);
buffer.append(", priority=");
buffer.append(priority);
buffer.append(", designation=");
buffer.append(designation);
buffer.append("]");
return buffer.toString();
}
@Override
public boolean equals(Object object) {
if (object == null)
return false;
if (object == this)
return true;
if (this.getClass() != object.getClass())
return false;
Employee employee = (Employee) object;
if (this.id == employee.getId()
this.firstName.equalsIgnoreCase(employee.getFirstName())
this.lastName.equalsIgnoreCase(employee.getLastName())
this.email.equalsIgnoreCase(employee.getEmail())
this.designation.equalsIgnoreCase(employee.getDesignation()))
return true;
return false;
}
@Override
public String toDisplayString() {
StringBuffer buffer = new StringBuffer();
buffer.append(this.getId());
buffer.append("\t");
buffer.append(this.getFirstName());
buffer.append("\t");
buffer.append(this.getLastName());
buffer.append("\t");
buffer.append(this.getEmail());
buffer.append("\t");
buffer.append(this.getDesignation());
return buffer.toString();
}
}
</pre>
<b>EmployeeService.java</b>
<pre class="brush:java">package com.jagadeesh.service;
import java.util.List;
import com.jagadeesh.domain.Employee;
public interface EmployeeService {
List&lt;Employee&gt; getAll();
void addEmployee(Employee employee);
}
</pre>
<b>EmployeeServiceImpl.java</b>
<pre class="brush:java">package com.jagadeesh.service.impl;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import com.jagadeesh.domain.Employee;
import com.jagadeesh.service.EmployeeService;
public class EmployeeServiceImpl implements EmployeeService {
private List&lt;Employee&gt; employees = new ArrayList&lt;Employee&gt;();
@Override
public List&lt;Employee&gt; getAll() {
List&lt;Employee&gt; employees = new ArrayList&lt;Employee&gt;(this.employees);
return Collections.unmodifiableList(employees);
}
@Override
public void addEmployee(Employee employee) {
if (employees.contains(employee)) {
System.out.println("Employee already exists");
} else {
this.employees.add(employee);
}
}
}
EmployeeIO.java
package com.jagadeesh.utils;
import java.util.List;
import com.jagadeesh.domain.Employee;
import com.jagadeesh.domain.impl.EmployeeImpl;
public class EmployeeIO {
public static Employee read() {
Employee employee = new EmployeeImpl();
employee.setId(KeyBoard.readInt("Enter Id :"));
employee.setFirstName(KeyBoard.read("Enter First Name :"));
employee.setLastName(KeyBoard.read("Enter Last Name :"));
employee.setEmail(KeyBoard.read("Enter Email :"));
employee.setDesignation(KeyBoard.read("Enter Designation :"));
return employee;
}
public static void out(List&lt;Employee&gt; employees) {
StringBuilder builder = new StringBuilder();
builder.append("Id\t\tFirst Name\t\tLast Name\t\tEmail\ttDesignation\n");
for (int i = 0; i &lt; employees.size(); i++) {
builder.append(employees.get(i).toDisplayString());
builder.append("\n");
}
System.out.println(builder);
}
}
KeyBoard.java
package com.jagadeesh.utils;
import java.util.Scanner;
public class KeyBoard {
public static int readInt(String message) {
System.out.print(message);
Scanner scanner = new Scanner(System.in);
try {
int number = Integer.parseInt(scanner.next());
return number;
}
catch(NumberFormatException e) {
System.out.println("Invalid Number");
return readInt(message);
}
}
public static String read(String message) {
System.out.print(message);
Scanner scanner = new Scanner(System.in);
return scanner.nextLine();
}
}
EmployeeMain.java
package com.jagadeesh.main;
import com.jagadeesh.domain.Employee;
import com.jagadeesh.service.EmployeeService;
import com.jagadeesh.service.impl.EmployeeServiceImpl;
import com.jagadeesh.utils.EmployeeIO;
import com.jagadeesh.utils.KeyBoard;
public class EmployeeMain {
public static void main(String[] args) throws Exception {
int option = 1;
EmployeeService empService = new EmployeeServiceImpl();
do {
Employee employee = EmployeeIO.read();
empService.addEmployee(employee);
option = KeyBoard.readInt(
"Do you want add another employee(1/0) :");
} while(option == 1);
System.out.println("Reading from List");
EmployeeIO.out(empService.getAll());
}
}
Out put of the program
Enter Id :1 Enter First Name :jagadeesh Enter Last Name :kumar Enter Email :[email protected] Enter Designation :developer Do you want add another employee(1/0) :1 Enter Id :2 Enter First Name :jagadeesh Enter Last Name :kumar Enter Email :[email protected] Enter Designation :developer Do you want add another employee(1/0) :1 Enter Id :1 Enter First Name :jagadeesh Enter Last Name :kumar Enter Email :[email protected] Enter Designation :developer Employee already exists Do you want add another employee(1/0) :testing invalid option Invalid Number Do you want add another employee(1/0) :1 Enter Id :3 Enter First Name :jagadeesh Enter Last Name :kumar Enter Email :[email protected] Enter Designation :developer Do you want add another employee(1/0) :0 Reading from List Id First Name Last Name Email Designation 1 jagadeesh kumar [email protected] developer 2 jagadeesh kumar [email protected] developer 3 jagadeesh kumar [email protected] developer