• JAVA 数组的常用操作


    目录:

    1. 声明数组;
    2. 初始化数组;
    3. 查看数组长度;
    4. 遍历数组;
    5. int数组转成string数组;
    6. 从array中创建arraylist;
    7. 数组中是否包含某一个值;
    8. 将数组转成set集合;
    9. 将数组转成list集合;
    10. Arrays.fill()填充数组;
    11. 数组排序;
    12. 复制数组;
    13. 比较两个数组;
    14. 去重复;
    15. 查询数组中的最大值和最小值;

    备注:文内代码具有关联性。

    1.声明数组;

    1 String [] arr;
    2 int arr1[];
    3 String[] array=new String[5];
    4 int score[]=new int[3];

    2.初始化数组;

     1 //静态初始化
     2 int arr2[]=new int[]{1,2,3,4,5};
     3 String[] array1={"马超","马云","关羽","刘备","张飞"};
     4 String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
     5 int score[]=new int[3];
     6 //动态初始化
     7 for(int i=0;i<score.length;i++)
     8 {   
     9   score[i]=i+1; 
    10 }

    3.查看数组长度;

    1 int length=array1.length;
    2 System.out.println("length:  "+array1.length);

    4.遍历数组;

    1 for (int i = 0; i < array1.length; i++) {
    2     System.out.println(array1[i]);
    3 }

    5.int数组转成string数组;

    1 int[]  array3={1,2,3,4,5,6,7,8,9,0};
    2         String arrStrings=Arrays.toString(array3);
    3         System.out.println(arrStrings);

    6.从array中创建arraylist;

    1 ArrayList<String> arrayList=new ArrayList<String>(Arrays.asList(array1));
    2 System.out.println(arrayList);

    7.数组中是否包含某一个值;

    1 String a="马超";
    2 String[] array1={"马超","马云","关羽","刘备","张飞"};
    3 if (Arrays.asList(array1).contains(a)) {
    4     System.out.println("马超在这里");
    5 }

    8.将数组转成set集合;

    1 String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
    2     Set<String> set=new HashSet<String>(Arrays.asList(array2));
    3     System.out.println(set);

    9.将数组转成list集合;

     1 String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
     2 //方法 1.
     3 List<String> list=new ArrayList<String>();
     4 for (int i = 0; i < array2.length; i++) {
     5     list.add(array2[i]);
     6 }
     7  
     8 String[] arrStrings2={"1","2","3"};
     9 //方法 2.
    10 List<String > list2=java.util.Arrays.asList(arrStrings2);
    11 System.out.println(list2);

    10.Arrays.fill()填充数组

    1 int[] arr3=new int[5];
    2         Arrays.fill(arr3, 10);  //将数组全部填充10
    3                //遍历输出
    4         for (int i = 0; i < arr3.length; i++) {
    5             System.out.println(arr3[i]);
    6         }

    11.数组排序;

     1 //方法 1.
     2 int[] arr4 = {3, 7, 2, 1, 9};
     3 Arrays.sort(arr4);         //.sort(int[] a)   放入数组名字
     4 for (int i = 0; i < arr4.length; i++) {
     5     System.out.println(arr4[i]);
     6 }
     7 //方法 2.        
     8 int[] arr5 = {3, 7, 2, 1, 9,3,45,7,8,8,3,2,65,34,5};
     9 Arrays.sort(arr5, 1, 4);  //.sort(a, fromIndex, toIndex)    从第几个到第几个之间的进行排序
    10 for (int i = 0; i < arr5.length; i++) {
    11         System.out.println(arr5[i]);
    12 }

    12.复制数组;

    1 //方法 1.
    2 int[] arr6 = {3, 7, 2, 1};
    3 int[] arr7=Arrays.copyOf(arr6, 10);  //指定新数组的长度
    4 //方法 2.        
    5 int[] arr8=Arrays.copyOfRange(arr6, 1, 3); //只复制从索引[1]到索引[3]之间的元素(不包括索引[3]的元素)
    6 for (int i = 0; i < arr8.length; i++) {
    7         System.out.println(arr8[i]);
    8

    13.比较两个数组;

    1 int[] arr9 = {1, 2, 3, 4,5,6,7,8,9,0};
    2         boolean arr10=Arrays.equals(arr6, arr9);
    3         System.out.println(arr10);

    14.去重复;

     1 int[] arr11 = {1, 2, 3, 4,5,6,7,8,9,0,3,2,4,5,6,7,4,32,2,1,1,4,6,3};
     2 //利用set的特性
     3 Set<Integer> set2=new HashSet<Integer>();
     4 for (int i = 0; i < arr11.length; i++) {
     5     set2.add(arr11[i]);
     6 }
     7 System.out.println(set2);
     8 int[] arr12 = new int[set2.size()];
     9 int j=0;
    10 for (Integer i:set2) {
    11     arr12[j++]=i;
    12 }
    13 System.out.println(Arrays.toString(arr12));

    15.查询数组中的最大值和最小值;

     1 int[] arr11 = {10, 2, 3, 4,5,6,7,8,9,0,3,2,4,5,6,7,4,32,2,1,1,4,6,3};
     2  //计算最大值
     3 int max = arr11[0];
     4 for (int i = 1; i < arr11.length; i++) {
     5      if (arr11[i] > max) {
     6          max = arr11[i];
     7     }
     8   }
     9   System.out.println("Max is " + max);
    10   //计算最小值
    11   int min = arr11[0];
    12   for (int i = 0; i < arr11.length; i++) {
    13     if (arr11[i]<min) {
    14         min = arr11[i];
    15     }
    16 }
    17   System.out.println("Min is " + min);
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  • 原文地址:https://www.cnblogs.com/lwx521/p/7544161.html
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