Type Inference with var (Java 10+)0%

Arithmetic, Assignment, Relational, and Logical Operators

Type Inference with var (Java 10+)

Beginner12 min read•Updated: 2026-10-22

🔍 Type Inference with var (Java 10+)

Introduction

Introduced in Java 10, Local Variable Type Inference allows developers to declare local variables using the var keyword, letting the compiler infer the exact type from the right-hand initialization expression.

⚡ Static Typing Remains Intact!

Critical Fact: var in Java is NOT like JavaScript's dynamic var. Java remains 100% statically typed. Once var is inferred at compile-time, its type is immutable and cannot change!

1import java.util.ArrayList;
2import java.util.HashMap;
3 
4public class VarDemo {
5    public static void main(String[] args) {
6        // Inferred types:
7        var studentAge = 22;                     // Inferred as int
8        var gpa = 8.75;                          // Inferred as double
9        var instituteName = "MSK Institute";     // Inferred as String
10 
11        // studentAge = "Twenty Two"; // 💥 Compiler Error: incompatible types: String cannot be converted to int
12 
13        // Eliminates boilerplate on complex generic types:
14        // Before: HashMap<String, ArrayList<Integer>> scores = new HashMap<String, ArrayList<Integer>>();
15        // With var:
16        var scores = new HashMap<String, ArrayList<Integer>>();
17 
18        System.out.println("Student: " + instituteName + ", Age: " + studentAge);
19    }
20}

🚫 Where `var` CANNOT Be Used

1
Class member variables (fields).
2
Method parameters or return types.
3
Variables declared without an immediate initializer (var x; is illegal).
4
Initialized with null (var x = null; is illegal).

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Arithmetic, Assignment, Relational, and Logical Operators

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Widening and Narrowing Type Casting & Type Safety	Arithmetic, Assignment, Relational, and Logical Operators

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Arithmetic, Assignment, Relational, and Logical Operators

Type Inference with var (Java 10+)

Beginner12 min read•Updated: 2026-10-22

Study Materials

🔍 Type Inference with var (Java 10+)

Introduction

⚡ Static Typing Remains Intact!

Critical Fact: var in Java is NOT like JavaScript's dynamic var. Java remains 100% statically typed. Once var is inferred at compile-time, its type is immutable and cannot change!

1import java.util.ArrayList;
2import java.util.HashMap;
3 
4public class VarDemo {
5    public static void main(String[] args) {
6        // Inferred types:
7        var studentAge = 22;                     // Inferred as int
8        var gpa = 8.75;                          // Inferred as double
9        var instituteName = "MSK Institute";     // Inferred as String
10 
11        // studentAge = "Twenty Two"; // 💥 Compiler Error: incompatible types: String cannot be converted to int
12 
13        // Eliminates boilerplate on complex generic types:
14        // Before: HashMap<String, ArrayList<Integer>> scores = new HashMap<String, ArrayList<Integer>>();
15        // With var:
16        var scores = new HashMap<String, ArrayList<Integer>>();
17 
18        System.out.println("Student: " + instituteName + ", Age: " + studentAge);
19    }
20}

🚫 Where `var` CANNOT Be Used

1
Class member variables (fields).
2
Method parameters or return types.
3
Variables declared without an immediate initializer (var x; is illegal).
4
Initialized with null (var x = null; is illegal).

Next Lesson

Arithmetic, Assignment, Relational, and Logical Operators

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Widening and Narrowing Type Casting & Type Safety	Arithmetic, Assignment, Relational, and Logical Operators

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

🔍 Type Inference with var (Java 10+)

Introduction

⚡ Static Typing Remains Intact!

🚫 Where var CANNOT Be Used

Arithmetic, Assignment, Relational, and Logical Operators

Related Lessons

Practice Quiz

Loading Page Content...

🔍 Type Inference with var (Java 10+)

Introduction

⚡ Static Typing Remains Intact!

🚫 Where var CANNOT Be Used

Arithmetic, Assignment, Relational, and Logical Operators

Related Lessons

Practice Quiz

🚫 Where `var` CANNOT Be Used

🚫 Where `var` CANNOT Be Used