Table of Contents
1 Introduction
2. The meaning of learning
2.1 Advantages and functions of Java collection framework
3. Interface
3.1 Basic relationship description
3.2 Collection interface description
3.3 Collection common methods
3.4 Collection example
3.5 Map interface description
3.6 Map example
4. Implementation
5.Framework
5.1. Use of collection framework
1. Introduction
Java
collection framework
Java Collection Framework
, also known as container
container
, is defined in
java.util
A set of interfaces under the package interfaces
and its implementation class
classes
.
Its main performance is to combine multiple elements
element
Placed in a single unit for quick and easy storage of these elements
store
Retrieve retrieve, manage
manipulate
, which is what we usually call addition, deletion, checking and modification
CRUD
.
For example, a deck of playing cards
(
a collection of cards
)
, a mailbox
(
A collection of emails
)
, an address book
(
Mapping relationship between a set of names and phone numbers
)
etc.
2. The meaning of learning
2.1 Advantages and functions of Java Collection framework
Using a mature collection framework helps us write efficient and stable code conveniently and quickly.
Learning the data structure knowledge behind it will help us understand the advantages, disadvantages and usage scenarios of each collection.
3. Interface
3.1 Basic relationship description
1.
Collection
: Used to store and manage a group of objects
objects
, these objects are generally called elements
elements
1.
Set
:
Elements cannot be repeated, and there is a hidden meaning behind them.
Find
/
Search
semantics
1.
SortedSet
:
An ordered set of non-repeating elements
2.
List
:
linear structure
3.
Queue
:
Queue
4.
Deque
:
deque
Tencent
–
Java
Backend development interview experience
1.
HashMap
Do you understand? Let me introduce it. If an object is
key
hour,
hashCode
and
equals
What should we pay attention to when using methods?
2.
HashSet
and
HashMap
What’s the difference?
3.
HashMap
Is it thread safe? So what does it take to require thread safety?
Alibaba
-Java
Backend development interview experience
1.ArrayList
and
LinkedList
What’s the difference?
2.
Have you ever understood
HashMap
Is it a specific implementation?
3. HashMap
and
ConcurrentHashMap
Which one is more efficient?
Today’s headlines
-Java
Backend development interview experience
1.
Programming question: Determine whether a linked list is a palindrome linked list.
2. Redis
of
zset
type corresponds to
java
What are the general types in the language?
3.hashCode
What is it mainly used for?
Description
boolean add(E e)
element
e
put in collection
void clear()
Remove all elements from the collection
boolean isEmpty()
Determine whether the set does not have any elements, commonly known as the empty set
boolean remove(Object e)
if element
e
appear in the collection, delete one of them
int size()
Returns the number of elements in the collection
Object[] toArray()
Returns an array containing all elements in the collection
2.
Map
:
key value pair
Key
–
Value
–
Pair
, hidden behind
Find
/
Search
semantics
1.
SortedMap
:
An ordered set of key-value pairs
3.2 Collection Interface Description
Collection (Java Platform SE 8)
3.3 Collection Common Methods
3.4 Collection Example
import java.util.Collection;
import java.util.ArrayList;
import java.util.Arrays;
public class Demo {
public static void main(String[] args) {
Collection<String> list = new ArrayList<>();
System.out.println(list.size());
System.out.println(list.isEmpty());
list.add("I");
list.add("love");
list.add("Java");
System.out.println(list.size());
System.out.println(list.isEmpty());
Object[] array = list.toArray();
System.out.println(Arrays.toString(array));
for (String s : list) {
System.out.println(s);
}
list.remove("love");
for (String s : list) {
System.out.println(s);
}
list.clear();
System.out.println(list.size());
System.out.println(list.isEmpty());
}
Description
V get(Object k)
According to the specified
k
Find the corresponding
v
V getOrDefault(Object k, V defaultValue)
According to the specified
k
Find the corresponding
v
, if not found, replace with default value
V put(K key, V value)
will specify
k-v
put into a
Map
boolean containsKey(Object key)
Determine whether it contains
key
boolean containsValue(Object value)
Determine whether it contains
value
Set
Return all key-value pairs
boolean isEmpty()
Determine whether it is empty
int size()
Returns the number of key-value pairs
operation result:
3.5 Map Interface Description
Map (Java Platform SE 8)
3.6 Map Example
import java.util.Map;
import java.util.HashMap;
public class Demo {
public static void main(String[] args) {
Map<String, String> map = new HashMap<>();
System.out.println(map.size());
System.out.println(map.isEmpty());
4. Implementation
Stack in java
System.out.println(map.get("author"));
System.out.println(map.getOrDefault("Author", "Anonymous"));
System.out.println(map.containsKey("author"));
System.out.println(map.containsValue("Anonymous"));
map.put("Author", "Lu Xun");
map.put("Title", "Madman's Diary");
map.put("Published time", "1918");
System.out.println(map.size());
System.out.println(map.isEmpty());
System.out.println(map.get("author"));
System.out.println(map.getOrDefault("Author", "Anonymous"));
System.out.println(map.containsKey("author"));
System.out.println(map.containsValue("Anonymous"));
for (Map.Entry<String, String> entry : map.entrySet()) {
System.out.println(entry.getKey());
System.out.println(entry.getValue());
}
}
}
0
true
null
Anonymous
false
false
3
false
Lu Xun
Lu Xun
true
false
author
Lu Xun
issuing time
1918
title
Diary of a Madman
5.Frame
5.1. Use of collection framework
1.
Collection
2.
List
3.
ArrayList
4.
LinkedList
5.
Stack
6.
Queue
7.
PriorityQueue
8.
Deque
9.
Set
10.
HashSet
11.
TreeSet
12.
Map
13.
HashMap
14.
TreeMap
15.
Collections
2.
The theory and implementation of data structures
1.
Sequence table
2.
linked list
3.
stack
4.
Queue
5.
Binary tree
6.
pile
3.
Sorting Algorithm
1.
insertion sort
2.
Hill sort
3.
selection sort
4.
Heap sort
5.
Bubble Sort
6.
Quick sort
7.
merge sort
4.Java
grammar
1.
Generics
Generic
2.
autoboxing
autobox
and automatic unboxing
autounbox
3.
Object
of
equals
method
4.
Comparable
and
Comparator
interface