Difference Between Shallow Copy and Deep Copy in Java

In Java, copying an object can be done in two ways: Shallow Copy and Deep Copy. These concepts are very important when working with object cloning and memory management.

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🔹 Shallow Copy

A Shallow Copy creates a new object but copies references of nested objects instead of creating new ones.

👉 Both original and copied objects refer to the same memory location for referenced objects.

Characteristics

• Copies primitive values directly
• Copies object references
• Faster performance
• Changes in referenced objects affect both copies

Example

java id="3fp8b0"
class Address {
    String city;
}

class Student implements Cloneable {
    int id;
    Address address;

    public Object clone() throws CloneNotSupportedException {
        return super.clone(); // Shallow copy
    }
}

🔹 Deep Copy

A Deep Copy creates a completely independent duplicate of the object including all referenced objects.

👉 Separate memory is allocated for all objects.

Characteristics

• Copies primitive values
• Creates new objects for references
• Safer but slightly slower
• Changes in one object do not affect the other

Example

java id="s8ld3v"
class Address {
    String city;
}

class Student implements Cloneable {
    int id;
    Address address;

    public Object clone() throws CloneNotSupportedException {
        Student s = (Student) super.clone();
        s.address = new Address();
        s.address.city = this.address.city;
        return s; // Deep copy
    }
}

🔹 Key Differences

Feature	Shallow Copy	Deep Copy
Object Creation	Partial copy	Complete copy
Reference Objects	Shared	Independent
Memory Usage	Less	More
Performance	Faster	Slightly slower
Data Safety	Low	High
Object Dependency	Linked	Fully separate

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