Java Collection Class Learning notes

The Java API is downloaded and can be queried in the API when the interface needs to be used.

1, Collection interface: Can be understood as a dynamic array of objects, the difference is that the contents of the object in the collection can be arbitrarily expanded.

Features: High performance, easy to expand and modify.

Common sub-class interfaces: List, Set, Queue.

2, the list interface has ArrayList, vector sub-class, the use of the same method, the difference is that ArrayList is asynchronous processing mode, high performance, but non-thread-safe, vector synchronous processing, low performance, but thread safety. Use the ArrayList subclass when thread safety is not required.

Usage examples:

Package com.webdashen.list;

Import java.util.ArrayList;
Import java.util.List;

public class Listdemo01 {

/**
* @param args
*/
public static void Main (string[] args) {
TODO auto-generated Method Stub
list<string> lists =null;
Lists=new arraylist<string> ();//interface cannot be instantiated and instantiated with its subclasses
Lists.add ("Hello");//Collection Object content arbitrary, and objects can be duplicated
Lists.add ("Xueshi");
Lists.add ("Xueshi");
for (int i=0;i<lists.size (); i++)
for (int i=0;i<2;i++)
{
System.out.println (Lists.get (i));
}
Lists.remove (2);//delete the specified Location object
System.out.println ("After Remove-----");
for (int i=0;i<lists.size (); i++)
for (int i=0;i<2;i++)
{
System.out.println (Lists.get (i));
}
System.out.println ("Whether the collection is empty:" +lists.isempty ());
System.out.println ("Xueshi exists:" +lists.indexof ("Xueshi"));
System.out.println ("Xue exists:" +lists.indexof ("Xue"));//These two statements can be tested to see how objects in the collection exist
}
}

Results:

Hello
Xueshi
Xueshi
After Remove-----
Hello
Xueshi
Whether the collection is empty: false
Xueshi exists: 1
Xue is present:-1

3, set, cannot add repeating elements, but can be sorted. Subclasses include HashSet (hash deposit), TreeSet (sequential storage).

Instance:

Package com.webdashen.list;

Import Java.util.HashSet;
Import Java.util.Set;

public class Setdemo01 {

/**
* @param args
*/
public static void Main (string[] args) {
TODO auto-generated Method Stub
set<string>s=null;
/*s=new treeset<string> ();
S.add ("B");
S.add ("A");
S.add ("C");
S.add ("D");
S.add ("E");
S.add ("F");
System.out.println (s); */
S=new hashset<string> ();
S.add ("A");
S.add ("B");
S.add ("C");
S.add ("D");
S.add ("E");
S.add ("F");
System.out.println (s);
}

}

4, Iterator interface: Specialized iterative output interface, the element is checked one after another, the content is removed.

5, MAP interface: stored in the form of key-value pairs, unordered, not allowed to repeat. Refer to the API introduction for specific use.

Java Collection Class Learning notes