The 10 most popular Java classes (GO)

Original: http://www.csdn.net/article/2012-06-04/2806277

Each Java programmer has a Java class ranking table of its own. This ranking table has no strict rules and no rules to follow, it depends entirely on the work of the Java project you are involved in. The following classes, without my introduction, are known to Java programmers because they are very popular in the Java world.

1. java.lang.String

No one can deny that the string class is undisputed champion. This is a final class that is used to create/manipulate immutable string literals. It's been there since JDK 1.0.

2. Java.lang.System

The use of the system class depends on the type of project you work on. You may not have used it in your project, but it is still one of the popular Java classes. This is a tool class that cannot be instantiated. The primary purpose of this class is to access standard input, output, environment variables, and so on. It is available starting from JDK 1.0.

3. Java.lang.Exception

Throwable is a superclass of all errors and exceptions. The handling of all exception cases belongs to the exception class. NullPointerException is the most popular among all the exceptions. The exception exception is at the top of all exception hierarchies. It is available starting from JDK 1.0.

4. Java.util.ArrayList

A class that implements the data structure of an array. This class implements the list interface and is a member of the most popular Java collection class. The difference between ArrayList and vectors is one of the common problems for beginners and is often asked in a Java interview. It has been introduced since JDK 1.2.

5. Java.util.HashMap

A class that implements key-value pairs of data structures. This class implements the map interface. Similar comparisons between ArrayList and Vector,hashmap and Hashtable are often taken. It is also a popular collection class, as a property-value container that is often used for data passing between multiple tiers of an application. It has been introduced since JDK 1.2.

6. Java.lang.Object

The root class for all Java classes. Each Java class is a subclass of the object class. Often used on the platform/frame. It contains some important methods, such as Equals, Hashcode, clone, ToString, and so on. It has been available since the first day of Java's birth (JDK 1.0)

7. Java.lang.Thread

A thread is a single-executed sequence in which multiple threads can exist together and share resources. We can extend the thread class and create our own threads. Of course, using runnable is another option. Whether to use this class depends on the needs of your application. A normal application is completely unnecessary to use threads. It has been introduced since JDK 1.0.

8. Java.lang.Class

Class is a subclass that inherits directly from the object class. This class has no constructors, and their objects are loaded by the Java virtual machine through the ClassLoader. Most of us may not have used it directly, but I think it is an important class to do reflection. It has been introduced since JDK 1.0.

9. Java.util.Date

This is the class used to process the date. Sometimes, we feel that this class should add more practical methods. Just as every enterprise application creates a utility unit of a date. It has been introduced since JDK 1.0, and later changed dramatically in JDK1.1, discarding a whole bunch of methods.

Ten. Java.util.Iterator

This is an interface. It is very popular and is used to replace enumerations. This is an easy-to-use unit that works synchronously with iterable. It has been introduced since JDK 1.2.

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English: Javapapers

Translation from: Oschina

The 10 most popular Java classes (GO)