55 What is hashCode() and Equals in java lang Object Class and How to Override their class in Java

How to generate identification number based on Contain?

Code:

package com.codingatharva;
class Student
{
int sid ;
String sname;

Student( int sid , String sname )  // Parameterized Constructor
{
this.sid = sid;
this.sname = sname;
}

/* Override toString() to print contain of object not address */
@Override
public String toString()
{
return sid+"...."+sname;
}

/* Override hashCode() to check memory based upon contain */
@Override
public int hashCode()
{
return sid+sname.hashCode();
}

/* Override equals method to check equality based upon contain rather
than object memory identification number */
@Override
public boolean equals( Object o )
{
Student s = (Student )o;
if( this.sid == s.sid && this.sname.equals(s.sname) )
{
return true;
}
else
{
return false;
}
}

public static void main(String args[] )
{
Student s1 = new Student( 101 , "Atharva Agrawal" );
Student s2 = new Student( 102 , "Coding  Atharva" );

System.out.println(" s1: "+s1+".."+s1.hashCode()+"\t"+System.identityHashCode(s1) );
System.out.println(" s2: "+s2+".."+s2.hashCode()+"\t"+System.identityHashCode(s2) );

Student s3 = new Student( 101 , "Atharva Agrawal" );
System.out.println(" s3: "+s3+".."+s3.hashCode()+"\t"+System.identityHashCode(s3) );

System.out.println("s1 and s2:  " + s1.equals(s2) );
System.out.println("s1 and s3:  "+ s1.equals(s3) );
}
}

Output:

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