What are immutable objects and Why is String Immutable

Code Examples

package com.javaninja.stringexamples;

import java.util.HashMap;

public class StringExample3 {
   //What are immutable objects and Why is String Immutable
public static void main (String args[])
{
String str1 = new String("Java");
System.out.println("str1 : "+str1);// Prints Java

str1.toUpperCase();
    System.out.println("str1 : "+str1);// Prints Java

    String str2= str1.toUpperCase();
    System.out.println("str2 : "+str2);// Prints JAVA
   
   
    Employee emp1 =  new Employee(101, "Vatsal");
    System.out.println("emp1 : "+emp1.getEmployeeCode()); // Prints 101
   
    emp1.setEmployeeCode(102);
    System.out.println("emp1 : "+emp1.getEmployeeCode()); // Prints 102
   
    HashMap hm = new HashMap();
    hm.put(str2, 1);
    str2=str2.concat(" Ninja");
    System.out.println(hm.get(str2));
   
}
}

package com.javaninja.stringexamples;

public class Employee {

private int employeeCode;

private String name;

Employee(int employeeCode,String name)

{

this.employeeCode = employeeCode;

this.name = name;

}

public int getEmployeeCode() {

return employeeCode;

}

public void setEmployeeCode(int employeeCode) {

this.employeeCode = employeeCode;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}