import Statement

The import statement in Java is used to make classes and interfaces from other packages accessible in the current source file without using their fully qualified names. It improves readability, maintainability, and developer productivity. This is a high-frequency interview topic, closely tied to packages and access control.

What Is the import Statement?

• Allows access to classes from other packages
• Eliminates need for fully qualified names
• Used at compile time
• Improves code clarity

import packageName.ClassName;
          

Why import Is Needed

Without import:

java.util.ArrayList list = new java.util.ArrayList();
          

With import:

import java.util.ArrayList;
ArrayList list = new ArrayList();
          

✔ Cleaner and more readable

Where import Statement Is Written

• After package statement
• Before class definition

package com.example.app;
import java.util.List;
import java.util.ArrayList;
public class Test { }
          

Types of import Statements

1️⃣ Single-Class Import

Imports one specific class.

import java.util.ArrayList;
          

• ✔ Most preferred
• ✔ Avoids ambiguity

2️⃣ Wildcard Import (*)

Imports all classes from a package.

import java.util.*;
          

• ⚠️ Does not import sub-packages
• ⚠️ May reduce readability

3️⃣ Static Import (Preview)

Imports static members of a class.

import static java.lang.Math.sqrt;
double r = sqrt(16);
          

✔ Used for constants and utility methods

Automatic Import (java.lang)

All classes in java.lang are automatically imported.

String s = "Java";
System.out.println(s);
          

✔ No import required

import vs Fully Qualified Name

✔ import does not impact performance

Import and Name Conflicts (Interview Favorite)

import java.util.Date;
import java.sql.Date;
          

❌ Compile-time error: ambiguous reference

Solution 1: Use Fully Qualified Name

java.util.Date d = new java.util.Date();
          

Solution 2: Import One, Qualify the Other

import java.util.Date;
java.sql.Date d2 = new java.sql.Date();
          

Multiple Imports in a File

• ✔ Allowed
• ✔ Order does not matter

import java.util.List;
import java.util.Map;
          

Importing User-Defined Packages

import com.mycompany.util.MathUtil;
          

✔ Same rules apply as built-in packages

Common Beginner Mistakes

• Forgetting import statement
• Assuming wildcard imports include sub-packages
• Importing unused classes
• Confusing static import with normal import
• Thinking imports increase runtime memory usage

Interview-Ready Answers

Short Answer

The import statement allows access to classes from other packages without using fully qualified names.

Detailed Answer

In Java, the import statement is used to make classes and interfaces from other packages available in the current source file. It improves code readability and is processed at compile time. The java.lang package is imported automatically.

Key Takeaway

import improves readability, not performance. Use specific imports for clarity and avoid wildcard imports unless justified.