详解Java中如何定义和访问静态字段和方法

public class MyClass {
    static int count;
    
    public void increase() {
        count++;
    }
}
 
MyClass obj1 = new MyClass();
obj1.increase();
 
MyClass obj2 = new MyClass();
System.out.println(obj2.count); // 输出 1，因为静态字段 count 是所有 MyClass 对象共享的。

public class MathHelper {
    public static final double PI = 3.1415926;
    
    public static double calculateCircleArea(double radius) {
        return Math.pow(radius, 2) * PI;
    }
}
 
double area = MathHelper.calculateCircleArea(5.0); // 计算半径为 5 的圆的面积
System.out.println(area); // 输出 78.53981633974483

import java.util.Arrays;
 
public class ArrayHelper {
    public static int[] reverse(int[] arr) {
        int[] reversedArr = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            reversedArr[i] = arr[arr.length - 1 - i];
        }
        return reversedArr;
    }
}
 
int[] arr = {1, 2, 3, 4};
int[] reversed = ArrayHelper.reverse(arr);
System.out.println(Arrays.toString(reversed)); // 输出 [4, 3, 2, 1]

import java.util.Arrays;
public class ArrayHelper {
    public static int[] reverse(int[] arr) {
        int[] reversedArr = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            reversedArr[i] = arr[arr.length - 1 - i];
        }
        return reversedArr;
    }
}
int[] arr = {1, 2, 3, 4};
int[] reversed = ArrayHelper.reverse(arr);
System.out.println(Arrays.toString(reversed)); // 输出 [4, 3, 2, 1]

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, world!");
    }
}