java经典题目2

18.做一个单子模式的类，只加载一次属性文件
package com.softeem.demo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
*@authorleno
*单子模式，保证在整个应用期间只加载一次配置属性文件
*/
publicclass Singleton {

privatestatic Singleton instance;
privatestaticfinal String CONFIG_FILE_PATH = "E://config.properties";
private Properties config;
private Singleton()
{
config = new Properties();
InputStream is;
try {
is = new FileInputStream(CONFIG_FILE_PATH);
config.load(is);
is.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
publicstatic Singleton getInstance()
{
if(instance==null)
{
instance = new Singleton();
}
returninstance;
}
public Properties getConfig() {
returnconfig;
}
publicvoid setConfig(Properties config) {
this.config = config;
}

}
l J2SE
19.拷贝一个目录(文件)到指定路径
/**
*拷贝一个目录或者文件到指定路径下
*@paramsource
*@paramtarget
*/
publicvoid copy(File source,File target)
{
File tarpath = new File(target,source.getName());
if(source.isDirectory())
{
tarpath.mkdir();
File[] dir = source.listFiles();
for (int i = 0; i < dir.length; i++) {
copy(dir[i],tarpath);
}
}else
{
try {
InputStream is = new FileInputStream(source);
OutputStream os = new FileOutputStream(tarpath);
byte[] buf = newbyte[1024];
int len = 0;
while((len = is.read(buf))!=-1)
{
os.write(buf,0,len);
}
is.close();
os.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
20.用JAVA中的多线程示例银行取款问题
packagecom.softeem.demo;

/**
*@authorleno
*账户类
*默认有余额，可以取款
*/
class Account {
privatefloatbalance = 1000;

publicfloat getBalance() {
returnbalance;
}

publicvoid setBalance(float balance) {
this.balance = balance;
}

/**
*取款的方法需要同步
*@parammoney
*/
publicsynchronizedvoid withdrawals(float money)
{
if(balance>=money)
{
System.out.println("被取走"+money+"元!");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
balance-=money;
}
else
{
System.out.println("对不起,余额不足!");
}
}

}

/**
*@authorleno
*银行卡
*/
class TestAccount1 extends Thread {

private Account account;

public TestAccount1(Account account) {
this.account = account;
}

@Override
publicvoid run() {
account.withdrawals(800);
System.out.println("余额为:"+account.getBalance()+"元!");
}
}
/**
*@authorleno
*存折
*/
class TestAccount2 extends Thread {

private Account account;
public TestAccount2(Account account) {
this.account = account;
}
@Override
publicvoid run() {
account.withdrawals(700);
System.out.println("余额为:"+account.getBalance()+"元!");
}
}

publicclass Test
{
publicstaticvoid main(String[] args) {
Account account = new Account();
TestAccount1 testAccount1 = new TestAccount1(account);
testAccount1.start();
TestAccount2 testAccount2 = new TestAccount2(account);
testAccount2.start();
}
}
21.用JAVA中的多线程示例火车站售票问题
package com.softeem.demo;

/**
*@authorleno
*售票类
*/
class SaleTicket implements Runnable {
inttickets = 100;

publicvoid run() {
while (tickets > 0) {
sale();
//或者下面这样实现
// synchronized (this) {
// if (tickets > 0) {
// System.out.println(Thread.currentThread().getName() + "卖第"
// + (100 - tickets + 1) + "张票");
// tickets--;
// }
// }
}
}

publicsynchronizedvoid sale() {
if (tickets > 0) {
System.out.println(Thread.currentThread().getName() + "卖第"
+ (100 - tickets + 1) + "张票");
tickets--;
}
}

}

publicclass TestSaleTicket {

publicstaticvoid main(String[] args) {
SaleTicket st = new SaleTicket();
new Thread(st, "一号窗口").start();
new Thread(st, "二号窗口").start();
new Thread(st, "三号窗口").start();
new Thread(st, "四号窗口").start();

}
}

22.用JAVA中的多线程示例生产者和消费者问题
package com.softeem.demo;

class Producer implements Runnable
{
private SyncStack stack;

public Producer(SyncStack stack) {
this.stack = stack;
}

publicvoid run() {
for (int i = 0; i < stack.getProducts().length; i++) {
String product = "产品"+i;
stack.push(product);
System.out.println("生产了: "+product);
try
{
Thread.sleep(200);
}
catch(InterruptedException e)
{
e.printStackTrace();
}

}
}

}

class Consumer implements Runnable
{
private SyncStack stack;

public Consumer(SyncStack stack) {
this.stack = stack;
}
publicvoid run() {
for(int i=0;i <stack.getProducts().length;i++)
{
String product =stack.pop();
System.out.println("消费了: "+product);
try
{
Thread.sleep(1000);
}
catch(InterruptedException e)
{
e.printStackTrace();
}

}

}
}

class SyncStack
{
private String[] products = new String[10];
privateintindex;
publicsynchronizedvoid push(String product)
{
if(index==product.length())
{
try {
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
notify();
products[index]=product;
index++;
}

publicsynchronized String pop()
{
if(index==0)
{
try {
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
notify();
index--;
String product = products[index];
return product;
}

public String[] getProducts() {
returnproducts;
}

}
publicclass TestProducerConsumer {

publicstaticvoid main(String[] args) {
SyncStack stack=new SyncStack();
Producer p=new Producer(stack);
Consumer c=new Consumer(stack);

new Thread(p).start();
new Thread(c).start();
}
}