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Java零基础入门Day4：数组与二维数组详解

news 2025/5/7 1:56:03

一、为什么需要数组？

当程序需要处理批量同类型数据时，使用多个变量存储会非常繁琐。例如存储70个学生姓名时，需定义70个变量，而数组可以简化这一过程，提高代码可维护性。

示例：变量存储的弊端

String name1 = "张誉";
String name2 = "刘疏桐";
// ... 定义70个变量
String name70 = "陈侃";

二、一维数组

1. 数组的定义与初始化

静态初始化：定义时直接赋值

// 完整格式
String[] names = new String[]{"张三", "李四", "王五", "赵六", "孙七", "周八", "吴九"};
// 简化格式
int[] scores = {85, 90, 78, 92, 88};

动态初始化：先定义长度，后赋值

double[] javaScores = new double[8]; // 定义长度为8的数组
javaScores[0] = 89.5; // 后续逐个赋值

2. 数组的访问与遍历

访问元素：通过索引（从0开始）

System.out.println(names[0]); // 输出：张三
names[1] = "田启峰"; // 修改元素

遍历数组

for (int i = 0; i < names.length; i++) {System.out.println(names[i]);
}

3. 常见应用案例

案例1：随机点名

String[] names = {"张三", "李四", "王五", "赵六", "孙七", "周八", "吴九"};
int index = (int) (Math.random() * names.length);
System.out.println(names[index] + "出来回答问题！");

案例2：统计成绩（最高分、最低分、平均分）

double[] scores = {85, 90, 78, 92, 88};
double max = scores[0], min = scores[0], sum = 0;for (double score : scores) {if (score > max) max = score;if (score < min) min = score;sum += score;
}
double avg = sum / scores.length;System.out.println("最高分：" + max);
System.out.println("最低分：" + min);
System.out.println("平均分：" + avg);

三、二维数组

1. 定义与初始化

静态初始化

String[][] seats = {{"张无忌", "赵敏", "周芷若"},{"张三丰", "宋远桥", "殷梨亭"},{"灭绝", "陈昆", "玄冥二老", "金毛狮王"},{"杨逍", "纪晓芙"}
};

动态初始化

int[][] matrix = new int[3][5]; // 3行5列的二维数组

2. 访问与遍历

访问元素

System.out.println(seats[0][1]); // 输出：赵敏
seats[2][2] = "谢逊"; // 修改元素

遍历二维数组

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

3. 应用案例：斗地主洗牌

// 初始化54张牌
String[] colors = {"♠", "♥", "♣", "♦"};
String[] numbers = {"3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A", "2"};
String[] poker = new String[54];
int index = 0;for (String number : numbers) {for (String color : colors) {poker[index++] = color + number;}
}
poker[52] = "小王";
poker[53] = "大王";// 洗牌：随机交换元素
Random rand = new Random();
for (int i = 0; i < poker.length; i++) {int swapIndex = rand.nextInt(poker.length);String temp = poker[i];poker[i] = poker[swapIndex];poker[swapIndex] = temp;
}