Overview of the "Core" framework in the Java class library
Overview of the "Core" framework in the Java class library
The "Core" framework in the Java library refers to the core library of Java. It provides a series of basic tool categories and data structures to support the development of Java programs.These core libraries are included in the standard library of Java (also known as the Java SE library) and are the basic components developed by Java.This article will introduce some common categories and functions in some core frameworks.
1. Object class:
The Object class is a parent class of all Java classes. It contains some basic methods, such as Equals (), Tostring (), and HashCode ().These methods can be used in all objects of Java and can be rewritten as needed.
Example code:
public class MyClass {
private int value;
public MyClass(int value) {
this.value = value;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || getClass() != obj.getClass()) {
return false;
}
MyClass myClass = (MyClass) obj;
return value == myClass.value;
}
@Override
public int hashCode() {
return Objects.hash(value);
}
@Override
public String toString() {
return "MyClass{" +
"value=" + value +
'}';
}
}
2. String class:
The String class is the core class used in Java to process string.It provides a series of methods for string operations, such as connection, interception and replacement of string.The String class is immutable, that is, the value cannot be modified after creation. Each time you operate String, a new String object is returned.
Example code:
String str1 = "Hello";
String str2 = "World";
String str3 = str1 + str2; // string connection
System.out.println (str3); // Output: HelloWorld
String substr = str3.substring (0, 5); // Trigger the sub -string
System.out.println (substr); // Output: Hello
3. Collection and Map interfaces:
The Collection interface is an interface that indicates a set of objects in Java. It provides methods for operating the set, such as adding, deleting and traversing.Common Collection subclasses include list, set, and queue.
The MAP interface is an interface used in Java to indicate the mapping of key values. It provides a series of methods for operating key value pairs, such as adding, deleting and finding.
Example code:
List<String> list = new ArrayList<>();
list.add("element1");
list.add("element2");
System.out.println (list.get (0)); // Output: Element1
Set<Integer> set = new HashSet<>();
set.add(1);
set.add(2);
System.out.println (set.contains (1)); // Output: true
Map<String, Integer> map = new HashMap<>();
map.put("key1", 1);
map.put("key2", 2);
System.out.println (map.get ("key1"); // Output: 1
Summarize:
The "Core" framework in the Java class library provides a series of basic tool categories and data structures that support the development of Java programs.By using these core libraries, we can more conveniently perform tasks such as object operation, string processing and collection management.These classes and interfaces are indispensable parts in the development of Java, which helps improve the reinnerstability and maintenance of the code.
