练习汇总1

练习汇总 数组练习 练习1：创建一个长度为6的int型数组，要求数组元素的值都在1-30之间，且是随机赋值。同时，要求元素的值各不相同。 public st
2023-11-24 技术

练习汇总

数组练习

  1. 练习1：创建一个长度为6的int型数组，要求数组元素的值都在1-30之间，且是随机赋值。同时，要求元素的值各不相同。

    public static void main(String[] args) {int[] array = new int[6];for (int i = 0; i < 6; i++) {array[i] = (int)(Math.random() * 30) + 1;for (int j = 0; j < i; j++) {if (array[i] == array[j]) {i--;break;				}}}for (int i = 0; i < array.length; i++) {System.out.println(array[i]);}
}

  2. 从键盘输入一个整数（1~20）

    则以该数字为矩阵的大小，把1,2,3…n*n 的数字按照顺时针螺旋的形式填入其中。例如： 输入数字2，则程序输出：

    1 2

    4 3

    输入数字3，则程序输出：

    1 2 3

    8 9 4

    7 6 5

    输入数字4， 则程序输出：

    1 2 3 4

    12 13 14 5

    11 16 15 6

    10 9 8 7

    public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("请输入一个数：");int length = scanner.nextInt();int [][] array = new int[length][length];// k = 1表示向右；k = 2表示向下；K = 3表示向左；k = 4表示向上int k = 1;int x = 0;int y = 0;for (int i = 1; i <= length * length; i++) {if (k == 1) {if (y < length && array[x][y] == 0) {array[x][y] = i;y++;} else {k = 2;x++;y--;i--;}} else if (k ==2) {if (x < length && array[x][y] == 0) {array[x][y] = i;x++;} else {k = 3;x--;y--;i--;}} else if (k ==3) {if (y >= 0 && array[x][y] == 0) {array[x][y] = i;y--;} else {k = 4;x--;y++;i--;}} else if (k ==4) {if (x >= 0 && array[x][y] == 0) {array[x][y] = i;x--;} else {k = 1;x++;y++;i--;}}}for (int i = 0; i < array.length; i++) {for (int j = 0; j < array[i].length; j++) {System.out.print(array[i][j] + " ");}System.out.println();}
}

  3. 使用简单数组
    (1)创建一个名为ArrayTest的类，在main()方法中声明array1和array2两个变量，他们是int[]类型的数组。
    (2)使用大括号{}，把array1初始化为8个素数：2,3,5,7,11,13,17,19。
    (3)显示array1的内容。
    (4)赋值array2变量等于array1，修改array2中的偶索引元素，使其等于索引值(如array[0]=0,array[2]=2)。打印出array1。
    思考：array1和array2是什么关系？
    拓展：修改题目，实现array2对array1数组的复制

    public static void main(String[] args) {int[] array1, array2;array1 = new int[]{2, 3, 5, 7, 11, 13, 17, 19};for (int i = 0; i < array1.length; i++){System.out.print(array1[i] + "\t");}System.out.println();//array2 = array1;不能实现复制//数组的复制array2 = new int[array1.length];for (int i = 0; i < array2.length; i++){array2[i] = array1[i];}for (int i = 0; i < array2.length; i += 2){array2[i] = i;}for (int i = 0; i < array1.length; i++){System.out.print(array1[i] + "\t");}
}

  4. 数组排序算法

    /*
冒泡排序：由小到大排序
*/
public static int[] bubbleSort(int[] array){for (int i = 0; i < array.length; i++){boolean flag = true;		//标志位，若一轮下来没有元素被交换，则表示该序列已有序for (int j = 0; j < array.length - i - 1; j++){if (array[j] > array[j + 1]){int temp = array[j + 1];array[j + 1] = array[j];array[j] = temp;flag = false;}}if (flage){break;}}
}

    /*
快速排序
*/
private static void swap(int[] data, int i, int j) {int temp = data[i];data[i] = data[j];data[j] = temp;}private static void subSort(int[] data, int start, int end) {if (start < end) {int base = data[start];int low = start;int high = end + 1;while (true) {while (low < end && data[++low] - base <= 0);while (high > start && data[--high] - base >= 0);if (low < high) {swap(data, low, high);} else {break;}}swap(data, start, high);subSort(data, start, high - 1);subSort(data, high + 1, end);}
}
public static void quickSort(int[] data){subSort(data,0,data.length-1);
}

  5. 数组查找算法

    /*
二分法查找
*/
public static int binarySearch(int[] array, int dest){int front = 0;int behind = array.length - 1;int mid;while (front <= behind){mid = (front + behind) / 2;if (dest > array[mid]){front = mid + 1;} else  if (dest < array[mid]){behind = mid - 1;} else if (dest == array[mid]) {return mid;}}return -1;
}

对象数组练习

  1. 定义类Student，包含三个属性：学号number(int)，年级state(int)，成绩score(int)。 创建20个学生对象，学号为1到20，年级和成绩都由随机数确定。
    问题一：打印出3年级(state值为3）的学生信息。
    问题二：使用冒泡排序按学生成绩排序，并遍历所有学生信息

    public class Exercise4 {public static void main(String[] args) {Student[] students = new Student[20];Exercise4 demo = new Exercise4();demo.initStudent(students, 20);demo.searchState(students, 3);demo.sortWithScore(students);demo.printInfo(students);}/*** * @Description 初始化对象数组* @author zbs* @date Jul 29, 20212:36:24 PM* @param students*/public void initStudent(Student[] students, int num) {for (int i = 0; i < num; i++) {students[i] = new Student();students[i].number = i + 1;students[i].score = (int)(Math.random() * 100) + 1;students[i].state = (int)(Math.random() * 6) + 1;}}/*** * @Description 根据年级进行查找* @author zbs* @date Jul 29, 20212:37:15 PM* @param students* @param state*/public void searchState(Student[] students, int state) {System.out.println("三年级的学生有：");System.out.println("学号\t成绩\t年级");for (int i = 0; i < students.length; i++) {if (students[i].state == state) {students[i].showInfo();}}}/*** * @Description 根据成绩进行排序* @author zbs* @date Jul 29, 20212:37:43 PM* @param students*/public void sortWithScore(Student[] students) {boolean flag;for (int i = 0; i < students.length; i++) {flag = true;for (int j = 0; j < students.length - i - 1; j++) {if (students[j].score > students[j + 1].score) {Student temp = students[j];students[j] = students[j + 1];students[j + 1] = temp;flag = false;}}if (flag) {break;}}}/*** * @Description 输出对象数组的信息* @author zbs* @date Jul 29, 20212:38:18 PM* @param students*/public void printInfo(Student[] students) {System.out.println("按成绩由小到大的排序为：");System.out.println("学号\t成绩\t年级");for (int i = 0; i < students.length; i++) {students[i].showInfo();}}
}class Student{/*** 学号*/int number;/*** 年级*/int state;/*** 分数*/int score;public void showInfo() {System.out.print(number + "\t");System.out.print(score + "\t");System.out.println(state + "\t");}
}

小实验1

  1. 自定义数组工具类

    public class ArrayUtil {/***返回数组的最大值ֵ* @Description * @author zbs* @date Jul 29, 20214:25:45 PM* @param array* @return*/public static int getMax(int[] array) {int max = array[0];for (int i = 1; i < array.length; i++) {if (array[i] > max) {max = array[i];}}return max;}/*** 返回数组的最小值ֵ* @Description * @author zbs* @date Jul 29, 20214:29:13 PM* @param array* @return*/public static int getMin(int[] array) {int min = array[0];for (int i = 1; i < array.length; i++) {if (array[i] < min) {min = array[i];}}return min;}/***返回数组的总和* @Description * @author zbs* @date Jul 29, 20214:34:02 PM* @param array* @return*/public static int getSum(int[] array) {int sum = 0;for (int i = 0; i < array.length; i++) {sum += array[i];}return sum;}/*** 返回数组的平均值ֵ* @Description * @author zbs* @date Jul 29, 20214:37:43 PM* @param array* @return*/public static double getAvarage(int[] array) {int sum = 0; for (int i = 0; i < array.length; i++) {sum += array[i];}return sum/array.length;}/*** 反转数组* @Description * @author zbs* @date Jul 29, 20214:41:50 PM* @param array*/public static void reverse(int[] array) {for (int i = 0; i < array.length / 2; i++) {int index = array.length - 1 - i;int temp = array[i];array[i] = array[index];array[index] = temp;}}/***复制数组* @Description * @author zbs* @date Jul 29, 20214:44:02 PM* @param array* @return*/public static int[] copy(int[] array) {int[] temp = new int[array.length];for (int i = 0; i < array.length; i++) {temp[i] = array[i];}return temp;}/*** 冒泡排序* @Description * @author zbs* @date Jul 29, 20214:48:23 PM* @param array*/public static void bullotSort(int[] array) {boolean flag;for (int i = 0; i < array.length - 1; i++) {flag = true;for (int j = 0; j < array.length - 1 - i; j++) {if (array[j] > array[j + 1]) {int temp = array[j];array[j] = array[j+1];array[j+1] = temp;flag = false;}}if (flag) {break;}}}/*** 输出数组内容* @Description * @author zbs* @date Jul 29, 20214:50:24 PM* @param array*/public static void toString(int[] array) {System.out.print("[");for (int i = 0; i < array.length - 1; i++) {System.out.print(array[i] + ",");}System.out.print(array[array.length - 1] + "]");}/*** 查找指定元素的位置* @Description * @author zbs* @date Jul 29, 20214:52:35 PM* @param array* @param dest* @return*/public static int getElem(int[] array, int dest) {for (int i = 0; i < array.length; i++) {if (array[i] == dest) {return i;}}return -1;}
}public class ArrayUtilTest {public static void main(String[] args) {int[] array = {1, 3, 5, 7, 9, 2, 4, 6, 8, 10};ArrayUtil.bullotSort(array);ArrayUtil.toString(array);}
}

构造器练习

  1. UML类图相关知识

    image-20210803140439742

  2. image-20210803144840990 
    public class Test{public static void main(String[] args) {Boy boy = new Boy("zbs", 20);Girl girl = new Girl("lhp", 19);boy.marry(girl);girl.marry(boy);}
}class Boy{private String name;private int age;public Boy(){}public Boy(String name){this.name = name;}public Boy(int age){this.age = age;}public Boy(String name, int age){this.name = name;this.age = age;}public void setName(String i){name = i;}public String getName(){return this.name;}public void setAge(int i){age = i;}public int getAge(){return this.age;}public void marry(Girl girl){System.out.println("我想娶" + girl.getName());}public void shout(){if (this.age >= 22){System.out.println("可以去结婚了");} else {System.out.println("再等等吧");}}
}class Girl{private String name;private int age;public Girl(){}public Girl(String name){this.name = name;}public Girl(int age){this.age = age;}public Girl(String name, int age){this.name = name;this.age = age;}public void setName(String i){name = i;}public String getName(){return this.name;}public void marry(Boy boy){System.out.println("我想嫁给" + boy.getName());boy.marry(this);}/*** @Description 比较两个对象的大小* @author zbs* @date Jul 29, 20212:38:18 PM* @param girl* @return 正数：当前对象大；负数：当前对象小；0：当前对象与形参对象相等*/public void compare(Girl girl){return this.age - girl.age;}
}

小实验2

  1. 根据下列要求书写代码：

    1. 按照如下的 UML 类图，创建相应的类，提供必要的结构
      image-20210803152544161

      在提款方法 withdraw()中，需要判断用户余额是否能够满足提款数额的要求，如果不能，应给出提示。deposit()方法表示存款。

    2. 按照如下的 UML 类图，创建相应的类，提供必要的结构
      image-20210803152702920

    3. 按照如下的 UML 类图，创建相应的类，提供必要的结构
      image-20210803152751885

      • addCustomer 方法必须依照参数（姓，名）构造一个新的 Customer 对象，然后把它放到 customer 数组中。还必须把 numberOfCustomer 属性的值加 1。

      • getNumOfCustomers 方法返回 numberofCustomers 属性值。

      • getCustomer 方法返回与给出的 index 参数相关的客户。

    4. 创建 BankTest 类，进行测试。

    public class Account{private double balance;public Account(double init_balance){this.balance = init_balance;} public double getBalance(){return this.balance;}public void deposit(double amt){if (amt >= 0){balance += amt;sysout("存钱成功！");} else {sysout("存钱数不能为负数！！");}}public void withdraw(double amt){if (balance >= amt){balance -= amt;sysout("取钱成功！");} else {sysout("余额不足，取钱失败！");}}
}

    public class Customer{private String firstName;private String lastName;private Account account;public Customer(String f, String l){this.firstName = f;this.lastName = l;}public String getFirstName(){return this.firstName;}public String getLastName(){return this.lastName;}public Account getAccount(){return this.account;}public void setAccount(Account acct){this.account = acct;}
}

    public class Bank{private Customer[] customers;private int numberOfCustomer;public Bank(){customers = new Customer[10];}public addCustomer(String f, String l){customers[numberOfCustomer++] = new Custemou(f, l);}public int getNumOfCustomers(){return this.numberOfCustomer;}public Customer getCustomer(int index){if (index < numberOfCustomer && index >= 0){return this.customers[index];            }return null;}
}

    public class Test{public static void main(String[] args){Bank bank = new Bank();bank.addCustomer("zhao", "binsheng");bank.getCustomer(0).setAccount(new Account(2000));bank.getCustomer(0).getAccount().withdraw(500);double balance = bank.getCustomer(0).getAccount().getBalance();System.out.println("客户：" + bank.getCustomer(0).getFirstName() + "的账户余额为：" + balance);}
}

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