JAVA数组

public class Main {
    public static void main(String[] args) {
        // char a[][]={{"ff"},{"ee"}};
        char c[][] = { { 'a', 'c' }, { 'c', 'd' } };
        String[][] list = { { "1", "张三" }, { "2", "李四" }, { "3", "王五" } };
        for (int i = 0; i < c.length; i++) {
            for (int j = 0; j < c[0].length; j++) {
                System.out.println(c[i][j]);
            }
        }
        System.out.println("..............");
        for (int i = 0; i < list.length; i++) {
            for (int j = 0; j < list[0].length; j++) {
                System.out.println(list[i][j]);
            }
        }
    }

}

public class Main {
    public static void main(String[] args) {
        // char a[][]={{"ff"},{"ee"}};
        char c[][] = new char[3][4];
        String[] list = { "1230", "ewfr", "sddf" };
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 4; j++) {
                c[i][j] = list[i].charAt(j);
            }
        }
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 4; j++) {
                System.out.println(c[i][j]);
            }
        }

    }
}

binarySearch()方法

https://blog.csdn.net/qpzkobe/article/details/78897762

 binarySearch(Object[], Object key)

a: 要搜索的数组

key：要搜索的值

如果key在数组中，则返回搜索值的索引

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Map<String, Integer> map = new HashMap<>();

        int nums[] = { 1, 2, 4, 8 };
        int index1 = Arrays.binarySearch(nums, 2);
        int index2 = Arrays.binarySearch(nums, 0);
        int index3 = Arrays.binarySearch(nums, 9);
        int index4 = Arrays.binarySearch(nums, 6);
        System.out.println("2: " + index1 + " 0: " + index2 + " 9: " + index3 + " 6: " + index4);

    }
}

System.arrayCopy

https://blog.csdn.net/qq_32405269/article/details/78374035

public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)
代码解释:
　　Object src : 原数组
   int srcPos : 从元数据的起始位置开始
　　Object dest : 目标数组
　　int destPos : 目标数组的开始起始位置
　　int length  : 要copy的数组的长度
Arrays.copyOfRange

 return Arrays.copyOfRange(a,0,cnt);//返回数组a【0，cnt)

Arrays.asList

https://blog.csdn.net/weixin_42585968/article/details/107465070

将数组转化为list

数组去重

   static public String[] qu(String[] a) {
        int cnt = 0;
        Set set = new HashSet<>();
        for (String x : a) {
            set.add(x);
        }
        Object[] ob = set.toArray();
        for (Object x : ob) {
            a[cnt++] = (String) x;
        }
        return Arrays.copyOfRange(a, 0, cnt);
    }