Java Collection Framework rule set--set

Collection:
Java supports three main types:
1. Rule set (SET)
Used to store a set of non-repeating elements
2. Linear table (list)
Used to store an ordered collection of elements
3. Queuing (queue)
A queue in the same data structure that stores the object in FIFO mode
Note: All interfaces and classes in the Java collection framework are stored in the Java.util package

Set
Set includes:
1. Hash set HashSet
2. Chain Hash Set Linkedhashset
3. Tree-Type set TreeSet
　　

HashSet:
1.HashSet belongs to the rule set, so it does not allow duplicate elements
2. The elements of a hash set do not have a specific order

1 ImportJava.util.*;2  Public classHashset_test {3      Public Static voidMain (string[] args) {4set<string> S1 =NewHashSet ();5S1.add ("Apple");6S1.add ("Huawei");7S1.add ("Samsung");8S1.add ("Apple");9 System.out.println (S1);TenHASHSET&LT;STRING&GT;S2 =NewHashSet (); OneS2.add ("Apple"); AS2.add ("Huawei"); -S2.add ("Samsung"); -S2.add ("Apple"); the System.out.println (S2); -     } -}

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1 [Apple, Samsung, Huawei] 2 [Apple, Samsung, Huawei]

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Linkedhashset:
It implements the extended HashSet class in the form of a linked list
1. It supports ordering elements within a rule set
2. It can be extracted in the order that the elements are inserted in the rule set
3. Belongs to the rule set, which does not allow duplicate elements

1  PackageOne ;2 ImportJava.util.LinkedHashSet;3 ImportJava.util.Set;4  Public classLinkedhashset_test {5      Public Static voidMain (string[] args) {6set<string> S1 =NewLinkedhashset ();7S1.add ("Apple");8S1.add ("Samsung");9S1.add ("Huawei");TenS1.add ("Apple"); One System.out.println (S1); A     } -}

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1 [Apple, Samsung, Huawei]

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TreeSet:
1. Provide more methods
2. You can ensure that the elements in the rule set are ordered
3. Belongs to the rule set, which does not allow duplicate elements

1  PackageOne ;2 ImportJava.util.Set;3 ImportJava.util.TreeSet;4  Public classTreeset_test {5      Public Static voidMain (string[] args) {6SET<STRING>S1 =NewTreeSet ();7S1.add ("Apple");8S1.add ("Samsung");9S1.add ("Huawei");TenS1.add ("Apple"); One System.out.println (S1); A     } -}

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1 [Apple, Huawei, Samsung]

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Summarize:

HashSet Sort by hash function

Linkedhashset Sort by Insertion Order

TreeSet in alphabetical order

HashSet: A hash table stores information by using a mechanism called hashing, and the elements are not stored in a particular order;
Linkedhashset: maintains a linked table of the collection in the order in which the elements are inserted, allowing iterations in the collection in the order in which they are inserted;
TreeSet: Provides an implementation that uses a tree structure to store a set interface, where objects are stored in ascending order, and the time to access and traverse is fast.

Java Collection Framework rule set--set