Core Java (5) Java Array

Array initialization and copying

Package COM. xujin; import Java. util. arrays; public class test {public static void main (string [] ARGs) {int [] A = {2, 3, 5, 7}; int [] B =; // At this time, a and B reference the same Array System. out. println (arrays. tostring (a); // [2, 3, 0, 7] system. out. println (arrays. tostring (B); // [2, 3, 0, 7] B = new int [] {12, 13, 14}; // initialize bsystem with an anonymous array. out. println (arrays. tostring (a); // [2, 3, 0, 7] system. out. println (arrays. tostring (B); // [12, 13, 14] // public static int [] copyof (INT [] original, int newlength) int [] C = arrays. copyof (A,. length); C [2] = 100; system. out. println (arrays. tostring (a); // [2, 3, 0, 7] system. out. println (arrays. tostring (c); // [2, 3,100, 7] // public static void arraycopy (Object SRC, int srcpos, object DEST, int destpos, int length) int [] d = {33, 44, 55, 66, 77, 88, 99}; system. arraycopy (D, 0, A, 1, 3); system. out. println (arrays. tostring (a); // [2, 33, 44, 55] system. out. println (arrays. tostring (d); // [33, 44, 55, 66, 77, 88, 99] // public static int [] copyofrange (INT [] original, int from, int to) int [] e = arrays. copyofrange (A, 1, 3); system. out. println (arrays. tostring (e); // [33, 44]}

Sorting of Arrays

In this test ~ 49 a total of 50 numbers can contain any 6 numbers. The output is sorted by size.

package com.xujin;import java.util.Arrays;public class Test {static final int MAX = 50;static final int FIT = 6;public static void main(String[] args){int[] total = new int[MAX];int[] result = new int[FIT];for(int i = 0; i < MAX; i++)total[i] = i;for(int i = 0; i < FIT; i++){result[i] = (int) (Math.random() * MAX);}Arrays.sort(result);System.out.println(Arrays.toString(result));}}

Test the binary search, filling, and determination of the same Array

Package COM. xujin; import Java. util. arrays; public class test {public static void main (string [] ARGs) {int [] A = new int [100]; for (INT I = 0; I <. length; I ++) A [I] = I; int [] B = arrays. copyofrange (A, 0, 10); system. out. println (arrays. tostring (B); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] // public static int binarysearch (INT [] A, int key) int r = arrays. binarysearch (A, 23); system. out. println (r); // 23 // public static void fill (INT [] A, int Val) arrays. fill (B, 8); system. out. println (arrays. tostring (B); // [8, 8, 8, 8, 8, 8, 8, 8, 8] // public static Boolean equals (INT [] A, int [] A2) int [] C = new int [] {8, 8, 8, 8, 8, 8, 8, 8, 8, 8}; If (arrays. equals (B, c) // returns a truesystem. out. println ("the two arrays are of the same size, and the same elements in the following table are equal ");}}

Two-dimensional array

Package COM. xujin; import Java. util. arrays; public class test {public static void main (string [] ARGs) {int [] [] matrix = {1, 2, 3}, {3, 2, 1}, {4, 5, 6 },}; system. out. println (Matrix [0] [2]); // 3for (INT I = 0; I <matrix. length; I ++) system. out. println (arrays. tostring (Matrix [I]); // [1, 2, 3] // [3, 2, 1] // [4, 5, 6] // quickly print a list of data elements in a two-dimensional array system. out. println (arrays. deeptostring (matrix); // [[1, 2, 3], [3, 2, 1], [4, 5, 6] // For each loop statements cannot automatically process every element of a two-dimensional array. They are for (INT [] row: matrix) for (INT value: row) {system. out. println (value * 10);}/* 102030302010405060 */}}

Irregular Array

Print the following series:

1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1 2 3 4 5 6
1 2 3 4 5 6 7
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9 10

package com.xujin;public class Test {public static void main(String[] args){int[][] test = new int[10][];for(int n = 0; n < 10; n++){test[n] = new int[n + 1];}for(int i = 0; i < 10; i++)for(int j = 0; j < test[i].length; j++){test[i][j] = j + 1;}for(int[] row : test){for(int value : row)System.out.print(value + " ");System.out.println();}}}

The above program creates an irregular array with 10 elements, respectively test [0] ~ Test [9], each element contains a different number of int types, test [0] contains 1, test [1] contains 2 .... test [9] contains 10