Java3个编程题整理
作者:互联网
1.代码实现单例模式中的懒汉模式
/**
* 单例模式中的懒汉模式
*/
public class LazySingleton {
/**
* 用volatile 修饰类变量
*/
private static volatile LazySingleton singleton;
/**
* 构造器私有
*/
private LazySingleton(){}
/**
* 双重检查
* @return
*/
public static LazySingleton getInstance(){
if(singleton == null){
synchronized (LazySingleton.class){
if(singleton == null){
singleton = new LazySingleton();
}
}
}
return singleton;
}
/**
* 测试
*/
public static void main(String[] args) {
LazySingleton singleton1 = LazySingleton.getInstance();
LazySingleton singleton2 = LazySingleton.getInstance();
System.out.println("singleton1:"+singleton1);
System.out.println("singleton2:"+singleton2);
System.out.println(singleton1 == singleton2);
}
}
2.编写一个Java程序在屏幕上输出1!+2!+3!+...+10!的和
public class Factorial {
/**
* 用遍历的方式解题
*/
public static void traverseMethod() {
int i, j, mul, sum = 0;
for (i = 1; i <= 10; i++) {
mul = 1;
for (j = 1; j <= i; j++) {
mul = mul * j;
}
sum = sum + mul;
}
System.out.println("1!+2!+3!+...+10!=" + sum);
}
/**
* 用递归的方式解题
*/
public static void factorialMethod() {
System.out.println("1!+2!+3!+...+10!="
+ (factorial(1) + factorial(2)
+ factorial(3) + factorial(4)
+ factorial(5) + factorial(6)
+ factorial(7) + factorial(8)
+ factorial(9) + factorial(10))
);
}
public static int factorial(int num) {
if (num == 1) {
return 1;
}
return num * factorial(num - 1);
}
/**
* 测试
*/
public static void main(String[] args) {
traverseMethod();//4037913
factorialMethod();//4037913
}
}
3.设计一个生产电脑和搬运电脑类,要求生产一台电脑就搬走一台电脑,如果没有新的电脑生产出来,则搬运工要等待新电脑产出;如果生产出的电脑没有搬走,则要等待电脑搬走之后在生产,并统计出生产的电脑数量。
public class ComputerTest {
public static void main(String[] args) throws InterruptedException {
Computer computer = new Computer();
Thread produceThread = new Thread(() -> {
for (int i = 0; i < 10; i++) {
try {
computer.produceComputer();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}, "produceThread");
produceThread.start();
Thread carryThread = new Thread(() -> {
for (int i = 0; i < 10; i++) {
try {
computer.carryComputer();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}, "carryThread");
carryThread.start();
produceThread.join();
carryThread.join();
System.out.printf("共生产了%s台电脑\n", computer.getComputerCount());
}
/**
* 电脑类
*/
public static class Computer {
/**
* 生产出的电脑的数量
*/
private int computerCount;
//电脑是否不为空 true-不为空 false为空
private volatile boolean flag;
/**
* 获取生产出的电脑的数量
*
* @return
*/
public int getComputerCount() {
return computerCount;
}
/**
* 生产电脑
*/
public synchronized void produceComputer() throws InterruptedException {
while (flag) {
wait();
}
this.computerCount++;
flag = true;
System.out.printf("%s 开始生产电脑\n", Thread.currentThread().getName());
notifyAll();
}
/**
* 搬运电脑
*/
public synchronized void carryComputer() throws InterruptedException {
//让搬运电脑消耗1秒钟,看程序执行效果
TimeUnit.SECONDS.sleep(1);
while (!flag) {
wait();
}
flag = false;
System.out.printf("%s 开始搬运电脑\n", Thread.currentThread().getName());
notifyAll();
}
}
}
标签:Thread,电脑,编程,LazySingleton,System,static,Java3,整理,public 来源: https://www.cnblogs.com/zhaoran8775/p/13071919.html