数组(Array)

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.Arrays;
 4 /**
 5  * 使用sort()方法对Java数组进行排序，及使用 insertElement () 方法向数组插入元素
 6  * 定义了 printArray() 方法来打印数组
 7  */
 8 public class ArrayAddAndGetLength {
 9     public static void main(String[] args) throws Exception {
10         int[] array = {2, 5, -2, 6, -3, 8, 0, -7, -9, 4};
11         Arrays.sort(array);
12         printArray("数组排序:", array);
13         int index = Arrays.binarySearch(array, 1);
14         System.out.println("元素 1 所在位置（负数为不存在）:" + index);
15         int newIndex = -index - 1;
16         array = insertElement(array, 1, newIndex);
17         printArray("数组添加元素 1", array);
18 
19         getArrayLength();
20     }
21 
22     private static void printArray(String message, int[] array) {
23         System.out.println(message + "[length:" + array.length + "]");
24         for (int i = 0; i < array.length; i++) {
25             if (i != 0) {
26                 System.out.print(", ");
27             }
28             System.out.print(array[i]);
29         }
30         System.out.println();
31     }
32 
33     private static int[] insertElement(int[] original, int element, int index) {
34         int length = original.length;
35         int[] destination = new int[length + 1];
36         System.arraycopy(original, 0, destination, 0, index);
37         destination[index] = element;
38         System.arraycopy(original, index, destination, index + 1, length - index);
39         return destination;
40     }
41     private static void getArrayLength(){
42         String[][] data = new String[2][5];
43         System.out.println("第一维数组长度:"+ data.length);
44         System.out.println("第二维数组长度：" + data[0].length);
45     }
46 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 /**
 4  * 在数组初始化后对数组进行扩容
 5  */
 6 public class ArrayBecomeBig {
 7     public static void main(String[] args){
 8         String[] names = new String[] {"a", "b", "c"};
 9         String[] extended = new String[5];
10         extended[3] = "d";
11         extended[4] = "e";
12         System.arraycopy(names, 0, extended, 0, names.length);
13         for (String str:extended){
14             System.out.println(str);
15         }
16     }
17 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.ArrayList;
 4 
 5 /**
 6  * 使用 remove () 方法来删除数组元素
 7  */
 8 public class ArrayDeleteFactor {
 9     public static void main(String[] args){
10      ArrayList objArray = new ArrayList();
11      objArray.clear();
12      objArray.add(0, "第0个元素");
13      objArray.add(1, "第1个元素");
14      objArray.add(2, "第2个元素");
15      System.out.println("删除前:" + objArray);
16      objArray.remove(1);
17      System.out.println("删除后:" + objArray);
18     }
19 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.*;
 4 
 5 /**
 6  * 通过 Collection 类的 Collection.max() 和 Collection.min() 方法来查找数组中的最大和最小值
 7  */
 8 public class ArrayGetMinAndMax {
 9     public static void main(String[] args){
10         Integer[] numbers = {8, 5, 6, 9, 10, 0, -2, 4};
11         int min = Collections.min(Arrays.asList(numbers));
12         int max = Collections.max(Arrays.asList(numbers));
13         System.out.println("最小值:" + min);
14         System.out.println("最大值:" + max);
15     }
16 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.Arrays;
 4 
 5 /**
 6  * 使用 equals ()方法来判断数组是否相等
 7  */
 8 public class ArrayIfSame {
 9     public static void main(String[] args){
10         int[] arr1 = {1, 2, 3, 4 ,5};
11         int[] arr2 = {1, 2, 3, 4 ,5};
12         int[] arr3 = {1, 2, 3};
13         System.out.println("数组 arr1 是否与数组 arr2 相等? : " + Arrays.equals(arr1, arr2));
14         System.out.println("数组 arr2 是否与数组 arr3 相等? : " + Arrays.equals(arr2, arr3));
15 
16     }
17 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.Arrays;
 4 import java.util.ArrayList;
 5 import java.util.List;
 6 
 7 /**
 8  * 通过 List 类的 Arrays.toString () 方法和 List 类的 list.Addall(array1.asList(array2) 方法将两个数组合并为一个数组
 9  */
10 public class ArrayMixAndInPut {
11     public static void main(String[] args){
12         ArrayMix();
13         ArrayInput();
14     }
15 
16     private static void ArrayMix(){
17         String[] a = {"A", "E", "I"};
18         String[] b = {"O", "U"};
19         List list = new ArrayList(Arrays.asList(a));
20         list.addAll(Arrays.asList(b));
21         Object[] c = list.toArray();
22         System.out.println(Arrays.toString(c));
23     }
24     //通过 Java Util 类的 Array.fill(arrayname,value) 方法和
25     // Array.fill(arrayname ,starting index ,ending index ,value) 方法向数组中填充元素
26     private static void ArrayInput(){
27         int[] array = new int[6];
28         Arrays.fill(array, 100);
29         for (int i = 0, n = array.length; i < n; i++){
30             System.out.println(array[i]);
31         }
32         System.out.println();
33         Arrays.fill(array, 3, 6, 50);
34         for (int i = 0, n = array.length; i < n; i++){
35             System.out.println(array[i]);
36         }
37     }
38 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.*;
 4 
 5 /**
 6  * 使用 Collections.reverse(ArrayList) 将数组进行反转
 7  */
 8 public class ArrayReverseAndOutput {
 9     public static void main(String[] args){
10         ArrayReverse();
11         ArrayOutput();
12     }
13 
14     private static void ArrayReverse(){
15         ArrayList arrayList = new ArrayList();
16         arrayList.add("A");
17         arrayList.add("B");
18         arrayList.add("C");
19         arrayList.add("D");
20         System.out.println("反转前数组:" + arrayList);
21         Collections.reverse(arrayList);
22         System.out.println("反转后数组:" + arrayList);
23     }
24 
25     private static void ArrayOutput(){
26         String[] StrArray = new String[3];
27         StrArray[0] = "hello";
28         StrArray[1] = "java";
29         StrArray[2] = "!";
30         for (String data:StrArray){
31             System.out.println(data);
32         }
33     }
34 
35 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.Arrays;
 4 
 5 /**
 6  * 1 使用sort()方法对Java数组进行排序
 7  * 2 使用 binarySearch() 方法来查找数组中的元素
 8  */
 9 public class ArraySearchAndSort {
10     public static void main(String[] args){
11         SortAndSearch();
12     }
13     private static void SortAndSearch(){
14         int[] array = {2, 5, -2, 6, -3, 8, 0, -7, -9, 4};
15         Arrays.sort(array);
16         printArray("数组的排序结果为", array);
17         int index = Arrays.binarySearch(array, 2);
18         System.out.println("元素 2 在第 [" + index + "] 个位置");
19     }
20     private static void printArray(String message, int[] array){
21         System.out.println(message + ":[length : " + array.length + "]");
22         for (int i = 0; i < array.length; i++){
23             if (i != 0){
24                 System.out.print(",");
25             }
26             System.out.print(array[i]);
27         }
28         System.out.println();
29     }
30 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.ArrayList;
 4 
 5 /**
 6  * 使用 contains () 方法来查找数组中的指定元素
 7  */
 8 public class ArraySearchFactor {
 9     public static void main(String[] args){
10         ArrayList objArray1 = new ArrayList();
11         ArrayList objArray2 = new ArrayList();
12         objArray2.add(0, "common1");
13         objArray2.add(1, "common2");
14         objArray2.add(2, "common3");
15         objArray1.add(0, "common1");
16         objArray1.add(1, "common2");
17         System.out.println("数组objArray1元素:" + objArray1);
18         System.out.println("数组objArray2元素:" + objArray2);
19         System.out.println("数组 objArray1 是否包含元素 common2 ? : " + objArray1.contains("common2"));
20         System.out.println("数组 objArray2 是否包含数组 objArray1 ? : " + objArray2.contains(objArray1));
21     }
22 }

 1 package JavaEE.JavaBaseExampleTest.Array;
 2 
 3 import java.util.ArrayList;
 4 import java.util.HashSet;
 5 import java.util.Set;
 6 
 7 public class ArraySubtractBothAnd extends Exception{
 8     public static void main(String[] args) {
 9         ArrayList objArray1 = new ArrayList();
10         ArrayList objArray2 = new ArrayList();
11         objArray2.add(0, "common1");
12         objArray2.add(1, "common2");
13         objArray2.add(2, "common3");
14         objArray2.add(3, "common5");
15         objArray1.add(0, "common1");
16         objArray1.add(1, "common2");
17         objArray1.add(3, "common3");
18         objArray1.add(2, "common4");
19         System.out.println("array1元素:" + objArray1);
20         System.out.println("array2元素:" + objArray2);
21         // 使用 removeAll () 方法来计算两个数组的差集
22         objArray1.removeAll(objArray2);
23         System.out.println("array1 和 array2 的差集为:" + objArray1);
24         // 使用 retainAll () 方法来计算两数组的交集
25         objArray1.retainAll(objArray2);
26         System.out.println("array1 和 array2 的交集为:" + objArray1);
27         BothArray();
28     }
29 
30     // 使用 union ()方法来计算两数组的并集
31     private static void BothArray(){
32         String[] arr1 = {"1", "2", "3"};
33         String[] arr2 = {"4", "5", "6"};
34         String[] resule_union = union(arr1, arr2);
35         System.out.println("并集结果如下:");
36         for (String str:resule_union){
37             System.out.println(str);
38         }
39     }
40     // 求两个字符串数组的并集，利用set的元素唯一性
41     private static String[] union(String[] arr1, String[] arr2){
42         Set<String> set = new HashSet<String>();
43         for (String str:arr1){set.add(str);}
44         for (String str:arr2){set.add(str);}
45         String[] result = { };
46         return set.toArray(result);
47     }
48 }