4) knowledge about JAVA containers and java containers
1> Array and Arrays: Arrays: A Tool class used to operate Arrays. It contains a set of static functions: equals (): Compares whether two Arrays are equal. Array has the same number of elements, and all corresponding elements are equal to each other.
Fill (): Enter the value in array. Sort (): used to sort arrays.
BinarySearch (): Search for elements in the sorted array.
System. arraycopy (): copying an array.
2> Collection and CollectionsCollections. max (Collection coll); obtain the largest element in the Collection.
Collections. sort (List list); sorts the elements in the list.
3> Design Pattern and iterator
Iterator: provides a method to sequentially aggregate elements of an object without exposing the internal representation of the object. Its main purpose is 1. different containers provide the same iterator interface. 2. this iterator interface is used when containers are used to access the content inside the container. 3. in this way, you only need to change the Declaration type when changing the container in use. The Code originally written for another container is still fully applicable to the new container.
Java iterator: It has simple functions and can only be moved one way.
(1) The method iterator () requires the container to return an Iterator. When the next () method of Iterator is called for the first time, it returns the first element of the sequence. Note: The iterator () method is a java. lang. Iterable interface inherited by Collection.
(2) Use next () to obtain the next element in the sequence.
(3) Use hasNext () to check whether there are any elements in the sequence.
(4) use remove () to delete the elements returned by the iterator.
Iterator is the simplest implementation of the Java Iterator. The ListIterator designed for List has more functions. It can traverse the List in two directions, or insert and delete elements from the List.
4> Comparable InterfaceIn the java. lang Package, the Comparable interface is applicable when a class has a natural order. Assuming that the object set is of the same type, this interface allows you to sort the set in a natural order. There are not many classes that implement the Comparable interface:
Class |
Sort |
BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, Short |
Sort by number |
Character |
Sort by numbers of Unicode values |
CollationKey |
Sort by language-sensitive strings |
Date |
Sort by generation |
File |
Sort by Unicode values of fully qualified characters of the system-specific path name |
ObjectStreamField |
Sort by Unicode values of Characters in the name |
String |
Sort by Unicode values in strings
|
