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Java.lang package in Java

Last Updated : 24 Jun, 2026

The java.lang package is one of the most fundamental packages in Java. This package provides essential functionality such as object manipulation, string handling, mathematical operations, exception handling, threading, and system-level operations.

Automatically imported by the Java compiler.
Contains core classes required by every Java program.
Provides support for strings, wrappers, threads, exceptions, and system operations.

Why is the `java.lang` Package Important?

It is automatically available in every Java program.
It contains the most commonly used classes in Java.
It provides the Object class, which is the parent of all Java classes.
It offers classes for working with strings, such as String and StringBuilder.
It provides mathematical functions through the Math class.
It supports exception handling using classes like Exception and Throwable.

Common Classes in java.lang

Class	Description
`Object`	Root superclass of all Java classes.
`String`	Represents an immutable sequence of characters.
StringBuilder	Mutable sequence of characters for efficient string manipulation.
StringBuffer	Thread-safe mutable sequence of characters.
`System`	Provides access to system resources, standard input/output, and environment variables.
`Math`	Contains methods for performing mathematical operations.
`Thread`	Represents a thread of execution in a Java program.
`Runnable`	Interface used to define tasks executed by threads.
`Exception`	Base class for exceptions that can be handled by applications.
`Error`	Represents serious system-level errors that applications typically do not handle.
`Throwable`	Superclass of both `Exception` and `Error`.
`Runtime`	Provides access to the Java runtime environment.
`Process`	Represents a process running in the operating system.
`Class`	Represents metadata about classes and interfaces at runtime.
`Integer`	Wrapper class for the primitive int type.
`Long`	Wrapper class for the primitive `long` type.
`Double`	Wrapper class for the primitive `double` type.
`Float`	Wrapper class for the primitive `float` type.
`Character`	Wrapper class for the primitive `char` type.
`Boolean`	Wrapper class for the primitive boolean type.
`Byte`	Wrapper class for the primitive `byte` type.
`Short`	Wrapper class for the primitive `short` type.
`Void`	Represents the `void` return type.
`Enum`	Base class for all Java enumerations.
`Package`	Contains information about Java packages.

Advantages of `java.lang` Package

Automatically Imported: No need to explicitly import the package in Java programs.
Provides Core Java Classes: Contains fundamental classes required for almost every Java application.
Supports Object-Oriented Programming: Includes the Object class, the root of the Java class hierarchy.
Simplifies String Handling: Offers classes like String, StringBuilder, and StringBuffer.
Built-in Mathematical Functions: The Math class provides common mathematical operations.
Exception Handling Support: Contains classes for handling exceptions and errors.
Multithreading Capabilities: Provides the Thread and Runnable classes.
Wrapper Class Support: Includes wrapper classes such as Integer, Double, and Boolean.
System-Level Operations: The System and Runtime classes allow interaction with the JVM and operating system.

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