What is Object Lifecycle in Java?

The Object Lifecycle in Java refers to the stages an object goes through from:

👉 Creation → Usage → Eligible for Garbage Collection → Destruction

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🔍 Stages of Object Lifecycle

1️⃣ Object Creation

An object is created using the new keyword.

class Student {
    String name;
}

Student s = new Student();

👉 Memory is allocated in heap memory, and the constructor is called.

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2️⃣ Object Usage

Once created, the object is used by calling methods or accessing variables.

s.name = "John";

👉 Object is actively used by the application.

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3️⃣ Object Becomes Eligible for Garbage Collection

An object becomes eligible for GC when it is no longer reachable.

💡 Example:

Student s1 = new Student();
s1 = null;

👉 Now the object has no reference → eligible for GC

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4️⃣ Garbage Collection

The JVM automatically removes unused objects using Garbage Collector (GC).

👉 This frees memory and improves performance.

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5️⃣ Object Destruction (Finalization)

Before removing the object, JVM may call:

protected void finalize() throws Throwable

⚠️ Note:

• finalize() is deprecated in modern Java

• Not guaranteed to execute

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🔄 Lifecycle Flow

Object Creation → Object Usage → No References → GC Eligible → Garbage Collection

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🧠 Types of Object Eligibility

Objects become eligible for GC in cases like:

• ✔️ Null reference

• ✔️ Reassigned reference

• ✔️ Out of scope

• ✔️ Anonymous objects

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💡 Example with Reassignment

Student s1 = new Student();
Student s2 = new Student();

s1 = s2;

👉 First object becomes eligible for GC

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🚀 Why Object Lifecycle is Important?

• ✔️ Helps in memory management

• ✔️ Avoids memory leaks

• ✔️ Improves performance

• ✔️ Important for real-time applications

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🎯 Interview Tip

👉 Common question:
When does an object become eligible for Garbage Collection?

✔️ Answer:
When it is no longer reachable by any active reference.

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