Java 案例大全(详细)一
一直在更新
- 案例汇总
-
- 比身高
- 判断奇偶数
- 考试评价
- 春夏秋冬
- 正反输出数据
- 求和1
- 逢七过
- 不死神兔
- 百钱买百鸡
- 输出所有时间
- 珠穆朗玛峰
- 求和2
- 猜数字
- 数组直接操作
- 比较最大值
- 获取最小值
- 数组内容相同
- 查找元素
- 反转元素
- 评委打分
- 用户登录
- 遍历字符串
- 统计字符次数
- 字符串的拼接1
- 字符串的拼接2
- 字符串反转1
- 字符串反转2
- 猫和狗1
- 猫和狗2
- 猫和狗3
案例汇总
比身高
三元运算符（?）
public class Test {
//案例：三个和尚比身高
public static void main(String args[]) {
//三元运算符的使用
int height1 = 160;
int height2 = 170;
int height3 = 180;
int result1 = height1 > height2 ? height1 : height2;
int result2 = result1 > height3 ? result1 : height3;
System.out.println("身高最高是：" + result2);
}
}
Scanner类
import java.util.Scanner;
public class Test {
//案例：三个和尚比身高
public static void main(String args[]) {
//Scanner类的使用
Scanner sc = new Scanner(System.in);
System.out.print("请输入第一个人的身高：");
int height1 = sc.nextInt();
System.out.print("请输入第二个人的身高：");
int height2 = sc.nextInt();
System.out.print("请输入第三个人的身高：");
int height3 = sc.nextInt();
int result1 = height1 > height2 ? height1 : height2;
int result2 = result1 > height3 ? result1 : height3;
System.out.println("身高最高的是：" + result2);
sc.close();
}
}
判断奇偶数
if … else …
import java.util.Scanner;
public class Test {
//案例：判断奇偶数
public static void main(String args[]) {
System.out.print("请输入一个数字：");
Scanner sc = new Scanner(System.in);
int number = sc.nextInt();
if (number % 2 == 0) {
System.out.println(number + " 是偶数");
}else {
System.out.println(number + " 是奇数");
}
sc.close();
}
}
考试评价
if……else if……else
import java.util.Scanner;
public class Test {
//案例：考试成绩
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("请输入你的考试成绩：");
int score = sc.nextInt();
if (score > 100 || score < 0) {
System.out.println("你输入的有误！！");
}else if (score > 90 && score <= 100) {
System.out.println("优秀！");
}else if (score > 80 && score <= 90) {
System.out.println("良好！");
}else if (score >= 60 && score <= 80) {
System.out.println("及格!!");
}else {
System.out.println("不及格！！！");
}
sc.close();
}
}
春夏秋冬
switch
import java.util.Scanner;
public class Test {
//案例：春夏秋冬
public static void main(String args[]) {
Scanner sc=new Scanner(System.in);
System.out.print("请输入对应的月份：");
int month=sc.nextInt();
switch(month) {
case 1:
System.out.println("冬季");
break;
case 2:
System.out.println("冬季");
break;
case 3:
System.out.println("春季");
break;
case 4:
System.out.println("春季");
break;
case 5:
System.out.println("春季");
break;
case 6:
System.out.println("夏季");
break;
case 7:
System.out.println("夏季");
break;
case 8:
System.out.println("夏季");
break;
case 9:
System.out.println("秋季");
break;
case 10:
System.out.println("秋季");
break;
case 11:
System.out.println("秋季");
break;
case 12:
System.out.println("冬季");
break;
default:
System.out.println("输入的数字有误！！");
}
sc.close();
}
}
补充 case穿透
import java.util.Scanner;
public class Test {
//案例：春夏秋冬
public static void main(String args[]) {
Scanner sc=new Scanner(System.in);
System.out.print("请输入对应的月份：");
int month=sc.nextInt();
switch(month) {
case 12:
case 1:
case 2:
System.out.println("冬季");
break;
case 3:
case 4:
case 5:
System.out.println("春季");
break;
case 6:
case 7:
case 8:
System.out.println("夏季");
break;
case 9:
case 10:
case 11:
System.out.println("秋季");
break;
default:
System.out.println("输入的数字有误！！");
}
sc.close();
}
}
正反输出数据
for 循环
public class Test {
//案例：正反输出数据
public static void main(String args[]) {
for(int i = 1;i <= 5; i++) {
// System.out.println(i);
System.out.print(i + " ");
}
System.out.println();
for(int i = 5; i >= 1; i--) {
System.out.print(i + " ");
}
}
}
求和1
100以内求和
public class Test {
//案例：100以内求和
public static void main(String args[]) {
int sum = 0;
for(int i = 1;i <= 100; i++) {
sum += i;
}
System.out.println("总共：" + sum);
}
}
求偶数和
public class Test {
//案例：100以内求偶数和
public static void main(String args[]) {
int sum=0;
for(int i = 1;i <= 100; i++) {
if(i % 2 == 0) {
sum += i;
}
}
System.out.println("偶数和为：" + sum);
}
}
求水仙花数
public class Test {
//案例：求水仙花数
//水仙花数是一个三位数，百位数，十位数，个位数的立方和等于它本身
public static void main(String args[]) {
int hunderds = 0, decade = 0, unit = 0;
int result = 0;
int count = 0; //计数
for(int i = 100; i < 1000; i++) {
hunderds = i / 100;
decade = i / 10 % 10;
unit = i % 10;
result = hunderds * hunderds * hunderds + decade * decade * decade + unit * unit * unit;
if(result == i) {
System.out.println(i);
count++;
}
}
System.out.println("总共：" + count + "个数");
}
}
逢七过
for 循环
public class Test {
//案例：逢七过
public static void main(String args[]) {
int count = 0;
for(int i = 1; i < 101; i++) {
if(i % 7 !=0 && i / 10 != 7 && i % 10 != 7) {
System.out.print(i + " ");
count++;
}
}
System.out.println("总共有：" + count + "个数");
}
}
不死神兔
for循环
public class Test {
//案例：不死神兔
//需求：有一对兔子，从出生后第三个月起每个月都生一对兔子，小兔子长到第三个月后每个月又生一对兔子，假如兔子都不死，问第二十个月的兔子对数为多少？
public static void main(String args[]) {
int arr[] = new int[20];
arr[0] = 1;
arr[1] = 1;
for(int i = 2; i < arr.length; i++) {
arr[i] = arr[i-2] + arr[i-1];
}
System.out.println("第二十个月为：" + arr[19]);
}
}
百钱买百鸡
for循环嵌套
public class Test {
//案例：百钱买百鸡
//需求：公鸡一只5文钱 母鸡一只3文钱 鸡仔3只一文钱
public static void main(String args[]) {
for (int i = 1; i < 21; i++) {
for (int j = 1; j < 34; j++) {
int z = 100 - i -j;
if ( z % 3 == 0 && i * 5 + j * 3 + z / 3 == 100 ) {
System.out.println("公鸡：" + i + "个，" +"母鸡：" + j + "个，" + "鸡仔" + z +"个");
}
}
}
}
}
输出所有时间
for循环嵌套
public class Test {
//案例：输出所有时间
public static void main(String args[]) {
for (int hours = 0; hours < 24; hours++) {
for (int minutes = 0; minutes < 60; minutes++) {
for (int seconds = 0; seconds < 60; seconds++) {
System.out.println(hours + " 时 " + minutes + " 分 " + seconds + " 秒 ");
}
}
}
}
}
珠穆朗玛峰
while循环
public class Test {
//案例：珠穆朗玛峰
public static void main(String args[]) {
//一张厚度为0.1cm足够大的纸，需要折叠多少次，才能达到珠穆朗玛峰高度8848860cm
long zf = 8848860;
double paper = 0.1;
int count = 0;
while ( paper < zf) {
paper *= 2;
count++;
}
System.out.println("折叠的次数为：" + count);
}
}
求和2
do……while循环
public class Test {
//案例：求和
public static void main(String args[]) {
int i = 5, sum = 0;
do {
i++;
sum += i;
} while (i < 10);
System.out.println("和为：" + sum);
}
}
猜数字
Random类使用
import java.util.Random;
import java.util.Scanner;
public class Test {
//案例：猜数字
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int number = 0;
Random r = new Random();
int num = r.nextInt(100) + 1; //随机产生1~100之间的数
while(true) {
System.out.print("请输入一个数字：");
number = sc.nextInt();
if (number > num) {
System.out.println("猜的数字大了！");
}else if(number < num) {
System.out.println("猜的数字小了！");
}else if(num == number){
System.out.println("恭喜你，猜对了！");
break;
}else{
System.out.println("输入的数字不合法！！");//java.util.InputMismatchException 不是数字，就会出报错！
}
}
sc.close();
}
}
数组直接操作
Arrays类
import java.util.Arrays;
public class Test {
public static void main(String[] args) {
int array1[] = {11, 1, 23, 55, 123};
System.out.println("原数组：" + Arrays.toString(array1));
int array2[] = {1, 2, 23, 55, 123};
int array3[] = {1, 11, 23, 55, 123};
Arrays.sort(array1);
System.out.println("排序后的数组为：" + Arrays.toString(array1));
int index = Arrays.binarySearch(array1, 23);
System.out.println("23元素所在位置：" + index);
// System.out.println("相同/不相同：" + array1.equals(array2));
System.out.println("相同/不相同：" + Arrays.equals(array1, array2));
System.out.println("数组2：" + Arrays.toString(array3));
System.out.println("相同/不相同：" + Arrays.equals(array1, array3));
Arrays.fill(array3, 2, 4, 1); //算头不算尾
System.out.println("修改后的数组2：" + Arrays.toString(array3));
}
}
比较最大值
数组操作1
public class Test {
//案例：比较最大值
public static void main(String args[]) {
int array[] = {1,2,3,4,5,6,7,8,9,10};
int max = array[0];
for(int i = 1; i < array.length; i++) {
if(max < array[i]) {
max = array[i];
}
}
System.out.println("最大值为：" + max);
}
}
获取最小值
数组操作2
public class Test {
//案例：获取最小值
public static void main(String args[]) {
int array[] = {1,2,3,4,5,6,7,8,9,10};
int min = array[0];
for(int i = 1; i < array.length; i++) {
if(min > array[i]) {
min = array[i];
}
}
System.out.println("最小值为：" + min);
}
}
数组内容相同
方法的使用
public class Test {
public static boolean compare(int arr1[], int arr2[]) {
boolean flag = true;
if (arr1.length == arr2.length) {
for (int i = 0; i < arr1.length; i++) {
if (arr1[i] != arr2[i]) {
flag = false;
break;
}
}
return flag;
} else {
return false;
}
}
//案例：数组内容相同
public static void main(String args[]) {
int arr1[] = {11, 22, 33, 44, 55};
int arr2[] = {11, 22, 33, 44, 55};
boolean flag = compare(arr1, arr2);
System.out.println("内容为：" + flag);
}
}
查找元素
方法使用
import java.util.Scanner;
public class Test {
public static int select(int arr[], int number) {
int index = -1;
for (int i = 0; i < arr.length; i++) {
if (number == arr[i]) {
index = i;
break;
}
}
return index;
}
//案例：查找元素
public static void main(String args[]) {
int arr[] = {1, 22, 33, 444, 555};
System.out.print("请输入你要查找的数：");
Scanner sc = new Scanner(System.in);
int number = sc.nextInt();
int index = select(arr, number);
System.out.println("元素在第" + index + "个位置");
sc.close();
}
}
反转元素
方法的使用
public class Test {
public static void reverse(int arr[]) {
for (int start = 0, end = arr.length - 1; start <= end; start++, end--) {
int temp = 0;
temp = arr[start];
arr[start] = arr[end];
arr[end] = temp;
}
}
public static void printArray(int arr[]) {
System.out.print("[");
for (int i = 0; i < arr.length; i++) {
if (i == arr.length - 1) {
System.out.print(arr[i]);
} else {
System.out.print(arr[i] + ",");
}
}
System.out.println("]");
}
//案例：反转元素
public static void main(String args[]) {
int arr[] = {1, 2, 3, 4, 5, 6};
reverse(arr);
printArray(arr);
}
}
评委打分
方法的使用
import java.util.Scanner;
public class Test {
public static int getMax(int arr[]) {
int max = arr[0];
for (int i=1; i < arr.length; i++) {
if (max < arr[i]) {
max = arr[i];
}
}
return max;
}
public static int getMin(int arr[]) {
int min = arr[0];
for (int i = 1; i < arr.length; i++) {
if (min > arr[i]) {
min = arr[i];
}
}
return min;
}
public static int getSum(int arr[]) {
int sum = 0;
for (int i = 0; i < arr.length; i++) {
sum += arr[i];
}
return sum;
}
//案例：评委打分
public static void main(String args[]) {
int arr[] = new int[6];
Scanner sc = new Scanner(System.in);
for (int i=0; i < arr.length; i++) {
System.out.print("请输入第" + (i+1) + "评委分数：");
arr[i] = sc.nextInt();
}
int max = getMax(arr);
int min = getMin(arr);
int sum = getSum(arr);
double average = (sum - max - min) / (arr.length - 2);
System.out.println("平均分为：" + average);
sc.close();
}
}
用户登录
字符串使用
import java.util.Scanner;
public class Test {
private static String userName="user";
private static String password="password";
//案例：用户登录
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
for (int i = 1; i <= 3; i++) {
System.out.print("请输入用户名：");
String username = sc.nextLine();
System.out.print("请输入密码：");
String pwd = sc.nextLine();
if (username.equals(userName) && pwd.equals(password)) {
System.out.println("登录成功");
break;
} else {
if (3-i == 0) {
System.out.println("账号已冻结！！");
} else {
System.out.println("你还有" + (3-i) + "次机会");
}
}
}
sc.close();
}
}
遍历字符串
字符串操作
import java.util.Scanner;
public class Test {
//案例：遍历字符串
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("请输入一个字符串：");
String string1 = sc.nextLine();
for (int i = 0; i < string1.length(); i++) {
if (i != string1.length() - 1) {
System.out.print(string1.charAt(i) + " ");
} else {
System.out.print(string1.charAt(i));
}
}
sc.close();
}
}
统计字符次数
字符串操作
import java.util.Scanner;
public class Test {
//案例：统计字符串次数
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("请输入一个字符串：");
String string1 = sc.nextLine();
int bigCount = 0,smallCount = 0,number = 0;
boolean flag = true;
for (int i = 0; i < string1.length(); i++) {
int temp = string1.charAt(i);
if (temp >= 'A' && temp <= 'Z') {
bigCount++;
} else if (temp >= 'a' && temp <= 'z'){
smallCount++;
} else if (temp >= '0' && temp <= '9') {
number++;
} else {
flag = false;
break;
}
}
if (flag) {
System.out.println("大写字母有：" + bigCount + "个，" + "小写字母有：" + smallCount + "个，" + "数字有：" + number + "个");
} else {
System.out.println("含中文字符！！");
}
sc.close();
}
}
字符串的拼接1
字符串操作
public class Test {
public static String arrayToString(int array[]) {
String string = "";
string += "[";
for (int i = 0; i < array.length; i++) {
if (i == array.length - 1) {
string += array[i];
} else {
string += array[i] + ",";
}
}
string += "]";
return string;
}
//案例：字符串的拼接
public static void main(String args[]) {
int array[] = {1,2,3,4,5};
String string = arrayToString(array);
System.out.println(string);
}
}
字符串的拼接2
StringBuilder类
public class Test {
public static String arrayToString(int array[]) {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("[");
for (int i = 0; i < array.length; i++) {
if (i == array.length - 1) {
stringBuilder.append(array[i]);
} else {
stringBuilder.append(array[i]).append(",");
}
}
stringBuilder.append("]");
return stringBuilder.toString();
}
//案例：字符串的拼接2
public static void main(String args[]) {
int array[] = {1, 2, 3, 4, 5};
String string = arrayToString(array);
System.out.println(string);
}
}
字符串反转1
字符串操作
import java.util.Scanner;
public class Test {
public static String reverse(String string) {
String str = "";
for (int i = string.length() - 1; i >= 0; i--) {
str += string.charAt(i);
}
return str;
}
//案例：字符串反转
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("请输入一个字符串：");
String string = sc.nextLine();
String str = reverse(string);
System.out.println(str);
sc.close();
}
}
字符串反转2
StringBuilder类
import java.util.Scanner;
public class Test {
public static String myReverse(String string) {
return new StringBuilder(string).reverse().toString();
}
//案例：字符串反转
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.print("请输入一个字符串：");
String string = sc.nextLine();
String str = myReverse(string);
System.out.println(str);
sc.close();
}
}
猫和狗1
多态的使用
public class Test{
/**
* 多态的弊端，不能使用子类的特有功能
* 案例：猫和狗 1
*/
public class Animal{
private String name;
private int age;
public Animal() {};
public Animal(String name,int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public void eat() {
System.out.println("动物吃东西");
}
public void show() {
System.out.println(getName() + " , " + getAge());
}
}
public class Pig extends Animal{
public Pig() {}
public Pig(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猪吃白菜");
}
}
public class Dog extends Animal{
public Dog() {}
public Dog(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("狗吃骨头");
}
}
public class Cat extends Animal{
public Cat() {}
public Cat(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猫吃鱼");
}
public void play() {
System.out.println("猫抓老鼠");
}
}
/**
* No enclosing instance of type Test is accessible.
* 非静态的内部类，要先实例化才能使用。
* @param args
*/
public static void main(String args[]) {
Test t = new Test(); //非静态的内部类，要先实例化才能使用。
Animal a = t.new Cat(); // 向上转型
a.setName("托马斯");
a.setAge(23);
a.eat();
a.show();
// Cat c = (Cat)a; //向下转型
a = t.new Cat("加菲猫", 11);
a.eat();
a.show();
// a.play(); //父类中并没有play方法
a = t.new Dog("二哈", 23);
a.eat();
a.show();
a = t.new Pig("皮猪", 13);
a.eat();
a.show();
}
}
猫和狗2
抽象类和抽象方法
public class Test{
/**
* 抽象类和抽象方法
* 案例：猫和狗 2
*/
public abstract class Animal{
private String name;
private int age;
public Animal() {};
public Animal(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public abstract void eat();
public void show() {
System.out.println(getName() + ", " + getAge());
}
}
public class Dog extends Animal {
public Dog() {}
public Dog(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("狗吃骨头");
}
}
public class Cat extends Animal {
public Cat() {}
public Cat(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猫吃鱼");
}
}
public class Pig extends Animal {
public Pig() {}
public Pig(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猪吃白菜");
}
}
public static void main(String[] args) {
Animal a = new Test().new Cat("加菲猫", 5);
a.eat();
a.show();
a = new Test().new Dog("藏獒", 10);
a.eat();
a.show();
a = new Test().new Pig("皮猪", 3);
a.eat();
a.show();
}
}
猫和狗3
接口使用
public class Test{
/**
* 接口
* 接口成员特点：成员变量只能是常量，默认public static final，无构造方法，成员方法只能是抽象方法，默认修饰public abstract
* 案例：猫和狗 3
*/
public interface Jumpping {
public abstract void jump();
}
public abstract class Animal implements Jumpping {
private String name;
private int age;
public Animal() {};
public Animal(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public abstract void eat();
public void show() {
System.out.println(getName() + ", " + getAge());
}
}
public class Dog extends Animal {
public Dog() {}
public Dog(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("藏獒吃骨头");
}
public void jump() {
System.out.println("藏獒跳远了");
}
}
public class Cat extends Animal {
public Cat() {}
public Cat(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猫吃鱼");
}
public void jump() {
System.out.println("猫可以跳高");
}
}
public class Pig extends Animal {
public Pig() {}
public Pig(String name, int age) {
super(name, age);
}
public void eat() {
System.out.println("猪吃白菜");
}
public void jump() {
System.out.println("猪跳高了");
}
}
public static void main(String[] args) {
Animal a = new Test().new Cat("加菲猫", 5); //a为一个对象句柄。
a.eat();
a.show();
a.jump();
a = new Test().new Dog("藏獒", 10);
a.eat();
a.show();
a.jump();
a = new Test().new Pig("皮猪", 3);
a.eat();
a.show();
a.jump();
}
}