java - 从一种方法在另一种方法中打印数组

Question

我创建了一个字符串数组和一个二维 double 组，并用initializeData() 方法内的值填充了这两个数组。现在我尝试在 displayData() 方法内显示数组。

我设法使用嵌套的 for 循环在initializeData() 中显示数据。

for(int i = 0; i<students.length; i++) {
        System.out.print(students[i] + "  ");
        for(int j = 0; j<grades.length; j++) {
            System.out.print(grades[i][j] + "   ");
        }
        System.out.println("");
    }

如何在 displayData() 中使用上面的相同循环并在方法initializeData() 中显示数组？

public class Assignment2 {
public static void main(String[] args) {
    initializeData();
    displayData();
}

/**
 * Method that initializes 5 students and grades for 5 courses and populates data.
 */
public static void initializeData() {
    //create arry with student names
    String[] students = {"James", "Luke", "Alex", "Jenny"};

    //create 2d array and populate it
    double grades[][] = {{98, 72, 85, 77, 90},{25,49,26,77,60},{13,8,46,52,28},{77,81,85,69,88}};
}

/**
 * Method that takes the data from initializeData() and displays it to the screen.
 */
public static void displayData() {

}

Answer 1

您的数组的范围仅限于初始化方法，并且您有两个对象，因此您不能将它们都返回到主方法，因此您唯一的选择(除了从初始化方法调用显示方法之外)是使用类变量将变量范围移动到整个类

import java.util.Arrays;
public class Assignment2 {

    static String[] students;
    static double[][]  grades;

    public static void main(String[] args) {
        initializeData();
        displayData();
    }

    /**
     * Method that initializes 5 students and grades for 5 courses and populates data.
     */
    public static void initializeData() {
        //create arry with student names
        students = new String[] {"James", "Luke", "Alex", "Jenny"};

        //create 2d array and populate it
        grades = new double[][] {{98, 72, 85, 77, 90},{25,49,26,77,60},{13,8,46,52,28},{77,81,85,69,88}};
    }

    /**
     * Method that takes the data from initializeData() and displays it to the screen.
     */
    public static void displayData() {
        System.out.println(Arrays.toString(students));
    }
} 

<小时/>

另一个选项包括这样的方法，但由您来了解自定义类

Student[] initializeData() {} 
void displayData(Student[] students) {} 

static void main (String[] args) {
    Student[] students = initializeData();
    displayData(students);
}