What are the built-in objects in java

The built-in objects in java include String, System, Out, In, Console, Math, Runtime, Thread, Exception, Throwable, Error, RuntimeException, SecurityManager, Class, Object, Package, InputStream, OutputStream, FileInputStream, etc. .

The operating system of this tutorial: Windows10 system, Java19.0.1 version, DELL G3 computer.

Built-in objects in Java refer to objects that come with the Java language and cannot be redefined. The following are some built-in objects in Java:

• String: String object, an object used to represent text data in Java.

• System: Provides a series of static methods that can be used for input/output, obtaining environment variables and other operations.

• Out: used for printing output, similar to System.out.

• In: used to obtain input, similar to System.in.

• Console: used for console input/output, similar to System.in and System.out, but more flexible.

• Math: Provides a series of mathematical functions and constants, such as trigonometric functions, exponential functions, logarithmic functions, etc.

• Runtime: used to obtain the current runtime environment and can be used to perform command line operations.

• Thread: Represents a thread object and can be used to create and manage threads.

• Exception: Exception handling class, used to capture and handle exceptions in the program.

• Throwable: The base class of all exception classes in Java, used to represent exceptions that can be thrown.

• Error: Indicates system-level errors, such as Java virtual machine errors, etc.

• RuntimeException: Indicates a runtime exception, which is an exception caused by a program error.

• SecurityManager: used for security management, which can restrict certain operations of the program, such as file access, network connections, etc.

• Class: Represents a class object and can be used to obtain class information and methods.

• Object: The base class of all classes, providing some common methods and properties, such as toString(), equals(), etc.

• Package: Represents a package object and can be used to obtain package information and methods.

• InputStream: Input stream class, used to read data.

• OutputStream: Output stream class, used to write data.

• FileInputStream and FileOutputStream: used for file read and write operations.

• BufferedInputStream and BufferedOutputStream: used to buffer read and write operations, which can improve read and write efficiency.

• DataInputStream and DataOutputStream: used to read and write basic data types and strings.

• ObjectInputStream and ObjectOutputStream: used to read and write objects.

• PrintStream: used for printing output, similar to System.out, but more flexible.

• Scanner: used to obtain input, similar to System.in, but more flexible.

• Random: Provides a random number generator that can generate various types of random numbers.

• Properties: Provides a property list that can be used for operations such as reading and writing configuration files.

• Timer: Provides timer function, which can be used for operations such as timer and time interval.

• Logger: Provides logging function, which can be used to record information when the program is running.

• TypeLiteral: Represents a type literal, which can be used for operations such as generic programming and type inference.

• Comparable interface and its implementation class: provide comparator function, which can be used for operations such as sorting and searching.

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