java简单内存图

class  Demo01
{
    public static void main(String[] args) 
    {
        //1.数据类型[] 数组名=new 数据类型[数组长度]
        int[] arr = new int[4];
        System.out.println(arr);
        arr[0]=99;
        arr[1]=98;
        arr[2]=97;
        //取数组元素的值
        /*System.out.println(arr[0]);
        System.out.println(arr[1]);
        System.out.println(arr[2]);
        System.out.println(arr[3]);*///0
}
}

class Demo03 
{
    public static void main(String[] args) 
    {    //1.数据类型[][] 数组名 = new 数据类型[大一维数组长度][小一维数组长度]
        /*int[][] arr = new int[3][2];
        arr[0][0]=99;
        arr[0][1]=100;
        arr[2][0]=88;
        System.out.println(arr[0][0]);
        System.out.println(arr[0][1]);
        System.out.println(arr[2][0]);
        System.out.println(arr[1][0]);
        System.out.println(arr[0]);
        System.out.println(arr);
}
}

double[][] arr = new double[3][];
            double[] arr1 = {1.2,1.6,1.8};
            double[] arr2 = {7.7,6.6};
            double[] arr3 = {1.3};
            arr[0]=arr1;
            arr[1]=arr2;
            arr[2]=arr3;
            System.out.println(arr[0][0]);

import java.util.Scanner;
class Demo05 
{
    public static void main(String[] args) 
    {
        double c = method01(1.8);
        System.out.println(c);
                double d = method01(12);
        System.out.println(d);
    }
    public static double method01(double a){
        double b=Math.PI*a*a;
        return b;
    }