Java in the basic operation of the array
In Java, all of the array has a default attribute length for access to the number of elements in an array.
1. Array replication: System.arraycopy ().
Such as:
Str1 int [] = new int [] (1,2,3);
Str2 int [] = new int [3]; / / invoked at the same address System.arraycopy (str1, 0, str2, 0, str1.length); / / Source Group of str1, str1 position of a start , copied to the target array str2, storage location, str2 from the first location, the store is a total length of 3 (also str1.length that can be used).
Note: If the target array, or other type of use, when the array of changes, the source array values have changed.
2. Array sort: Arrays.sort (). (In the java.util package)
Such as:
Int [] num = new int [] (3,1,2);
Arrays.sort (num);
For (int i = 0; i <num.length; i + +)
(
System.out.println (num [i]) / / output 1,2,3, in descending order.
)
If participation is the sort of target, the target must be achieved Comparable interface through compareTo method to compare engagement sort element.
As follows:
Student ss [] [] = (new Student new Student (1, "zhangsan")
New Student (2, "lisi")
New Student (3, "wangwu")
New Student (3, "mybole"));
Arrays.sort (ss);
For (int i = 0; i <ss.length; i + +)
(
System.out.println (ss [i]);
)
………………………………
Sclass Student implements Comparable
(
Int num;
String name;
Student (int num, String name)
(
This.num = num;
This.name = name;
)
Public String toString ()
(
Return "number =" + num +","+" name = "+ name;
)
Public int compareTo (Object o)
(
Student s = (Student) o;
/ / Return num> s.num? 1: (num == s.num? 0: -1) / / num according to the rules of the sort object
/ / The following: If num is equally divided, according to sort name
Int result = num> s.num? 1: (num == s.num? 0: -1);
If (0 == result)
(
Result = name.compareTo (s.name); / / String has achieved the compareTo method
)
Return result;
)
)
3. Has sort of a certain element of the array View: Arrays.binarySearch ().
As indicated above:
Arrays.binarySearch int index = (num, 3); / / num by an array of digital 3 Index
System.out.println ( "index =" + index); / / output 2
System.out.println ( "element =" + num [index]); / / 3
