How to Make a class Immutable?

Don’t provide “setter” methods or methods that modify fields or objects referred to by fields.

Make all fieldsfinalandprivate.

Prevent overriding

The best way to prevent overriding is declaring your class as afinal class.

Factory method instance creation and Private Constructor

Never pass the reference of the Mutable objects

Let put all these and create the immutable class.

public final class ImmutableClassExample

{

//Both String and Integer is Immutable

private final String val1;

private final Integer val2;

//Date is a Mutable field

private final Date date1;

public ImmutableClassExample(String val1,Integer val2,Date date1)

{

this.val1=val1;

this.val2=val2;

this.date1=new Date(date1.getTime());

}

public String getVal1()

{

return val1;

}

public Integer getVal2()

{

return val2;

}

public Date getDate()

{

return new Date(date1.getTime());

}

public static ImmutableClassExample getImmutableClassExampleObject(String a,Integer b,Date c)

{

return new ImmutableClassExample(a,b,c);

}

public String toString()

{

return val1+" --- "+val2+" --- "+date1;

}

}