数组

数组

数组声明与创建

package Study2;

public class ArrayDemo {
    //变量类型  变量名字 = 变量数值；
    public static void main(String[] args) {
        int[] num; //首选方法

        int num2[]; //不推荐，c与c++的过度方法 //声明数组
        num = new int[10];//这里面可以存放10个int类型数字 //创建数组
        //给数组元素赋值
        num[0] = 1;
        num[1] = 2;
        num[2] = 3;
        num[3] = 4;
        num[4] = 5;
        num[5] = 6;
        num[6] = 7;
        num[7] = 8;
        num[8] = 9;
        num[9] = 10;
        //计算总和
        int sum = 0;
        for (int i = 0; i < num.length; i++) { //遍历数组
            sum += num[i];
        }
        System.out.println(sum);
    }
}

初始化及内存分析

数组基本特点

数组越界

ArrayIndexOutOfBonce

数组使用

for each 循环

直接打 arrays.for 即可出现

package Study2;

public class ArrayDemo3 {
    public static void main(String[] args) {
        int array[] = {1,2,3,4,5,6,7,8};
       // for (int i : array) {
         //   System.out.println(array[i]);
            //反转数组
            int result[] = new int[array.length];
        for (int i = 0,j=array.length-1; i < array.length; i++,j--) {
                result[j] =array[i];
                System.out.println(result[j]);
            }
        }
    }

arrays类使用

冒泡排序算法

package Study2;
import java.util.*;
public class ArrayDemo4 {
    public static void main(String[] args) {
        int[] a = {3, 5, 6, 7, 9, 1, 2, 55, 67, 87, 12, 33, 44, 56, 9};
        int[] sort= sort(a);
        System.out.println(Arrays.toString(sort));
    }
    public static int[] sort(int[]array) {
        int temp=0;
        for (int i = 0; i < array.length-1; i++) {
            for (int j = 0; j < array.length-1-i; j++) {
                if (array[j]>array[j+1]){   //大的下沉
                    temp=array[j];
                    array[j]=array[j+1];
                    array[j+1]=temp;
                }
            }
        }
        return array;
    }
}

稀疏数组