Import Statements in Java

Every class has a full name such as java.util.ArrayList. Writing that each time would be tiring, so an import statement at the top of the file lets you use the short name instead. An import is purely a convenience for the compiler: it doesn't copy code, load anything or slow your program down. It just tells the compiler, "when I write ArrayList, I mean java.util.ArrayList".

Three Ways to Refer to a Class

import java.util.ArrayList;
import java.util.List;
 
public class Imports {
    public static void main(String[] args) {
        List<String> names = new ArrayList<>();
        names.add("Navika");
        names.add("Srihitha");
        names.add("Advitha");
        System.out.println(String.join(", ", names));
 
        java.time.LocalDate republicDay = java.time.LocalDate.of(2026, 1, 26);
        System.out.println("Republic Day 2026: " + republicDay.getDayOfWeek());
    }
}

Navika, Srihitha, Advitha
Republic Day 2026: MONDAY

How it works

1. import java.util.ArrayList; and import java.util.List; are single-type imports: each brings in one class.
2. String needs no import: everything in java.lang is imported automatically.
3. java.time.LocalDate is written with its fully qualified name and no import. That's handy when you use a class once, or when two classes share a name.

Try it yourself: replace the two imports with import java.util.*;. Does it still compile?

Single-Type vs Wildcard

A wildcard covers one package only. import java.util.*; does not import java.util.function.Function; sub-packages are separate packages.

Neither form affects speed or the size of the .class file: the compiler records only the classes you actually use. Most teams prefer single-type imports because they show exactly where each class comes from, and IDEs manage them automatically.

Name Clashes

Both java.util and java.sql have a class named Date. With two wildcards, a plain Date is ambiguous:

import java.util.*;
import java.sql.*;
 
public class Dates {
    Date today;
}

Dates.java:5: error: reference to Date is ambiguous
    Date today;
    ^
  both class java.sql.Date in java.sql and class java.util.Date in java.util match
1 error

Two fixes:

1. Add a single-type import, import java.util.Date;. A single-type import beats wildcards.
2. Write the full name where you need the other one: java.sql.Date sqlDate.

What import Does Not Do

Common Mistakes

Expecting import java.util.* to include sub-packages. java.util.function and java.util.concurrent need their own imports.

Importing a class from the unnamed (default) package. It's impossible; put the class in a named package.

Putting imports before the package line. The order is: package, then imports, then types.

Interview Corner

Practice

1. Easy: Write a program that uses Scanner, ArrayList and LocalDate, with one single-type import for each.
2. Harder: Write a class that needs both java.util.Date and java.sql.Date. Import one and use the full name for the other.

Key Takeaways