需求50句以上的JAVA代码，并带注解

Java文件操作大全

1创建文件夹

//import javaio;

File myFolderPath = new File(%%1);

try {

if (!myFolderPathexists()) {

myFolderPathmkdir();

}

}

catch (Exception e) {

Systemoutprintln("新建目录操作出错");

eprintStackTrace();

}

2创建文件

//import javaio;

File myFilePath = new File(%%1);

try {

if (!myFilePathexists()) {

myFilePathcreateNewFile();

}

FileWriter resultFile = new FileWriter(myFilePath);

PrintWriter myFile = new PrintWriter(resultFile);

myFileprintln(%%2);

resultFileclose();

}

catch (Exception e) {

Systemoutprintln("新建文件操作出错");

eprintStackTrace();

}

3删除文件

//import javaio;

File myDelFile = new File(%%1);

try {

myDelFiledelete();

}

catch (Exception e) {

Systemoutprintln("删除文件操作出错");

eprintStackTrace();

}

4删除文件夹

//import javaio;

File delFolderPath = new File(%%1);

try {

delFolderPathdelete(); //删除空文件夹

}

catch (Exception e) {

Systemoutprintln("删除文件夹操作出错");

eprintStackTrace();

}

5删除一个文件下夹所有的文件夹

//import javaio;

File delfile=new File(%%1);

File[] files=delfilelistFiles();

for(int i=0;i<fileslength;i++){

if(files[i]isDirectory()){

files[i]delete();

}

}

6清空文件夹

//import javaio;

File delfilefolder=new File(%%1);

try {

if (!delfilefolderexists()) {

delfilefolderdelete();

}

delfilefoldermkdir();

}

catch (Exception e) {

Systemoutprintln("清空目录操作出错");

eprintStackTrace();

}

7读取文件

//import javaio;

// 逐行读取数据

FileReader fr = new FileReader(%%1);

BufferedReader br = new BufferedReader(fr);

String %%2 = brreadLine();

while (%%2 != null) {

%%3

%%2 = brreadLine();

}

brclose();

frclose();

8写入文件

//import javaio;

// 将数据写入文件

try {

FileWriter fw = new FileWriter(%%1);

fwwrite(%%2);

fwflush();

fwclose();

} catch (IOException e) {

eprintStackTrace();

}

9写入随机文件

//import javaio;

try {

RandomAcessFile logFile=new RandomAcessFile(%%1,"rw");

long lg=logFilelength();

logFileseek(%%2);

logFilewriteByte(%%3);

}catch(IOException ioe){

Systemoutprintln("无法写入文件："+ioegetMessage());

}

10读取文件属性

//import javaio;

// 文件属性的取得

File af = new File(%%1);

if (afexists()) {

Systemoutprintln(fgetName() + "的属性如下： 文件长度为：" + flength());

Systemoutprintln(fisFile() "是文件" : "不是文件");

Systemoutprintln(fisDirectory() "是目录" : "不是目录");

Systemoutprintln(fcanRead() "可读取" : "不");

Systemoutprintln(fcanWrite() "是隐藏文件" : "");

Systemoutprintln("文件夹的最后修改日期为：" + new Date(flastModified()));

} else {

Systemoutprintln(fgetName() + "的属性如下：");

Systemoutprintln(fisFile() "是文件" : "不是文件");

Systemoutprintln(fisDirectory() "是目录" : "不是目录");

Systemoutprintln(fcanRead() "可读取" : "不");

Systemoutprintln(fcanWrite() "是隐藏文件" : "");

Systemoutprintln("文件的最后修改日期为：" + new Date(flastModified()));

}

if(fcanRead()){

%%2

}

if(fcanWrite()){

%%3

}

11写入属性

//import javaio;

File filereadonly=new File(%%1);

try {

boolean b=filereadonlysetReadOnly();

}

catch (Exception e) {

Systemoutprintln("拒绝写访问："+eprintStackTrace());

}

12枚举一个文件夹中的所有文件

//import javaio;

//import javautil;

LinkedList<String> folderList = new LinkedList<String>();

folderListadd(%%1);

while (folderListsize() > 0) {

File file = new File(folderListpeek());

folderListremoveLast();

File[] files = filelistFiles();

ArrayList<File> fileList = new ArrayList<File>();

for (int i = 0; i < fileslength; i++) {

if (files[i]isDirectory()) {

folderListadd(files[i]getPath());

} else {

fileListadd(files[i]);

}

}

for (File f : fileList) {

%%2=fgetAbsoluteFile();

%%3

}

}

13复制文件夹

//import javaio;

//import javautil;

LinkedList<String> folderList = new LinkedList<String>();

folderListadd(%%1);

LinkedList<String> folderList2 = new LinkedList<String>();

folderList2add(%%2+ %%1substring(%%1lastIndexOf("\\")));

while (folderListsize() > 0) {

(new File(folderList2peek()))mkdirs(); // 如果文件夹不存在 则建立新文件夹

File folders = new File(folderListpeek());

String[] file = folderslist();

File temp = null;

try {

for (int i = 0; i < filelength; i++) {

if (folderListpeek()endsWith(Fileseparator)) {

temp = new File(folderListpeek() + Fileseparator

+ file[i]);

} else {

temp = new File(folderListpeek() + Fileseparator

+ file[i]);

}

if (tempisFile()) {

FileInputStream input = new FileInputStream(temp);

FileOutputStream output = new FileOutputStream(

folderList2peek() + Fileseparator

+ (tempgetName())toString());

byte[] b = new byte[5120];

int len;

while ((len = inputread(b)) != -1) {

outputwrite(b, 0, len);

}

outputflush();

outputclose();

inputclose();

}

if (tempisDirectory()) {// 如果是子文件夹

for (File f : templistFiles()) {

if (fisDirectory()) {

folderListadd(fgetPath());

folderList2add(folderList2peek()

+ Fileseparator + fgetName());

}

}

}

}

} catch (Exception e) {

//Systemoutprintln("复制整个文件夹内容操作出错");

eprintStackTrace();

}

folderListremoveFirst();

folderList2removeFirst();

}

14复制一个文件夹下所有的文件夹到另一个文件夹下

//import javaio;

//import javautil;

File copyfolders=new File(%%1);

File[] copyfoldersList=copyfolderslistFiles();

for(int k=0;k<copyfoldersListlength;k++){

if(copyfoldersList[k]isDirectory()){

ArrayList<String>folderList=new ArrayList<String>();

folderListadd(copyfoldersList[k]getPath());

ArrayList<String>folderList2=new ArrayList<String>();

folderList2add(%%2+"/"+copyfoldersList[k]getName());

for(int j=0;j<folderListlength;j++){

(new File(folderList2get(j)))mkdirs(); //如果文件夹不存在 则建立新文件夹

File folders=new File(folderListget(j));

String[] file=folderslist();

File temp=null;

try {

for (int i = 0; i < filelength; i++) {

if(folderListget(j)endsWith(Fileseparator)){

temp=new File(folderListget(j)+"/"+file[i]);

}

else{

temp=new File(folderListget(j)+"/"+Fileseparator+file[i]);

}

FileInputStream input = new FileInputStream(temp);

if(tempisFile()){

FileInputStream input = new FileInputStream(temp);

FileOutputStream output = new FileOutputStream(folderList2get(j) + "/" +

(tempgetName())toString());

byte[] b = new byte[5120];

int len;

while ( (len = inputread(b)) != -1) {

outputwrite(b, 0, len);

}

outputflush();

outputclose();

inputclose();

}

if(tempisDirectory()){//如果是子文件夹

folderListadd(folderListget(j)+"/"+file[i]);

folderList2add(folderList2get(j)+"/"+file[i]);

}

}

}

catch (Exception e) {

Systemoutprintln("复制整个文件夹内容操作出错");

eprintStackTrace();

}

}

}

}

15移动文件夹

//import javaio;

//import javautil;

LinkedList<String> folderList = new LinkedList<String>();

folderListadd(%%1);

LinkedList<String> folderList2 = new LinkedList<String>();

folderList2add(%%2 + %%1substring(%%1lastIndexOf("\\")));

while (folderListsize() > 0) {

(new File(folderList2peek()))mkdirs(); // 如果文件夹不存在 则建立新文件夹

File folders = new File(folderListpeek());

String[] file = folderslist();

File temp = null;

try {

for (int i = 0; i < filelength; i++) {

if (folderListpeek()endsWith(Fileseparator)) {

temp = new File(folderListpeek() + Fileseparator

+ file[i]);

} else {

temp = new File(folderListpeek() + Fileseparator

+ file[i]);

}

if (tempisFile()) {

FileInputStream input = new FileInputStream(temp);

FileOutputStream output = new FileOutputStream(

folderList2peek() + Fileseparator

+ (tempgetName())toString());

byte[] b = new byte[5120];

int len;

while ((len = inputread(b)) != -1) {

outputwrite(b, 0, len);

}

outputflush();

outputclose();

inputclose();

if (!tempdelete())

Systemoutprintln("删除单个文件操作出错!");

}

if (tempisDirectory()) {// 如果是子文件夹

for (File f : templistFiles()) {

if (fisDirectory()) {

folderListadd(fgetPath());

folderList2add(folderList2peek()

+ Fileseparator + fgetName());

}

}

}

}

} catch (Exception e) {

// Systemoutprintln("复制整个文件夹内容操作出错");

eprintStackTrace();

}

folderListremoveFirst();

folderList2removeFirst();

}

File f = new File(%%1);

if (!fdelete()) {

for (File file : flistFiles()) {

if (filelist()length == 0) {

Systemoutprintln(filegetPath());

filedelete();

}

}

}

16移动一个文件夹下所有的文件夹到另一个目录下

//import javaio;

//import javautil;

File movefolders=new File(%%1);

File[] movefoldersList=movefolderslistFiles();

for(int k=0;k<movefoldersListlength;k++){

if(movefoldersList[k]isDirectory()){

ArrayList<String>folderList=new ArrayList<String>();

folderListadd(movefoldersList[k]getPath());

ArrayList<String>folderList2=new ArrayList<String>();

folderList2add(%%2+"/"+movefoldersList[k]getName());

for(int j=0;j<folderListlength;j++){

(new File(folderList2get(j)))mkdirs(); //如果文件夹不存在 则建立新文件夹

File folders=new File(folderListget(j));

String[] file=folderslist();

File temp=null;

try {

for (int i = 0; i < filelength; i++) {

if(folderListget(j)endsWith(Fileseparator)){

temp=new File(folderListget(j)+"/"+file[i]);

}

else{

temp=new File(folderListget(j)+"/"+Fileseparator+file[i]);

}

FileInputStream input = new FileInputStream(temp);

if(tempisFile()){

FileInputStream input = new FileInputStream(temp);

FileOutputStream output = new FileOutputStream(folderList2get(j) + "/" +

(tempgetName())toString());

byte[] b = new byte[5120];

int len;

while ( (len = inputread(b)) != -1) {

outputwrite(b, 0, len);

}

outputflush();

outputclose();

inputclose();

tempdelete();

}

if(tempisDirectory()){//如果是子文件夹

folderListadd(folderListget(j)+"/"+file[i]);

folderList2add(folderList2get(j)+"/"+file[i]);

}

}

}

catch (Exception e) {

Systemoutprintln("复制整个文件夹内容操作出错");

eprintStackTrace();

}

}

movefoldersList[k]delete();

}

}

17以一个文件夹的框架在另一个目录创建文件夹和空文件

//import javaio;

//import javautil;

boolean b=false;//不创建空文件

ArrayList<String>folderList=new ArrayList<String>();

folderListadd(%%1);

ArrayList<String>folderList2=new ArrayList<String>();

folderList2add(%%2);

for(int j=0;j<folderListlength;j++){

(new File(folderList2get(j)))mkdirs(); //如果文件夹不存在 则建立新文件夹

File folders=new File(folderListget(j));

String[] file=folderslist();

File temp=null;

try {

for (int i = 0; i < filelength; i++) {

if(folderListget(j)endsWith(Fileseparator)){

temp=new File(folderListget(j)+"/"+file[i]);

}

else{

temp=new File(folderListget(j)+"/"+Fileseparator+file[i]);

}

FileInputStream input = new FileInputStream(temp);

if(tempisFile()){

if (b) tempcreateNewFile();

}

if(tempisDirectory()){//如果是子文件夹

folderListadd(folderListget(j)+"/"+file[i]);

folderList2add(folderList2get(j)+"/"+file[i]);

}

}

}

catch (Exception e) {

Systemoutprintln("复制整个文件夹内容操作出错");

eprintStackTrace();

}

}

18复制文件

//import javaio;

int bytesum = 0;

int byteread = 0;

File oldfile = new File(%%1);

try {

if (oldfileexists()) { //文件存在时

FileInputStream inStream = new FileInputStream(oldfile); //读入原文件

FileOutputStream fs = new FileOutputStream(new File(%%2,oldfilegetName()));

byte[] buffer = new byte[5120];

int length;

while ( (byteread = inStreamread(buffer)) != -1) {

bytesum += byteread; //字节数 文件大小

Systemoutprintln(bytesum);

fswrite(buffer, 0, byteread);

}

inStreamclose();

}

}

catch (Exception e) {

Systemoutprintln("复制单个文件操作出错");

eprintStackTrace();

}

19复制一个文件夹下所有的文件到另一个目录

//import javaio;

File copyfiles=new File(%%1);

File[] files=copyfileslistFiles();

for(int i=0;i<fileslength;i++){

if(!files[i]isDirectory()){

int bytesum = 0;

int byteread = 0;

try {

InputStream inStream = new FileInputStream(files[i]); //读入原文件

FileOutputStream fs = new FileOutputStream(new File(%%2,files[i]getName());

byte[] buffer = new byte[5120];

int length;

while ( (byteread = inStreamread(buffer)) != -1) {

bytesum += byteread; //字节数 文件大小

Systemoutprintln(bytesum);

fswrite(buffer, 0, byteread);

}

inStreamclose();

} catch (Exception e) {

Systemoutprintln("复制单个文件操作出错");

eprintStackTrace();

}

}

}

20提取扩展名

String %%2=%%1substring(%%1lastIndexOf("")+1);

Coursejava

public class Course {

    private String name;//课程名

    private String id; //编号

    private String selectId; //选修课编号

    public String getName() {

        return name;

    }

    public void setName(String name) {

        thisname = name;

    }

    public String getId() {

        return id;

    }

    public void setId(String id) {

        thisid = id;

    }

    public String getSelectId() {

        return selectId;

    }

    public void setSelectId(String selectId) {

        thisselectId = selectId;

    }

}

1、i=0循环后，number=1 price=9 money=19+0=9

i=1循环后，number=2 price=8 money=28+9=25

i=2跳出循环

输出money=25

2、选b

以下是规定r=Mathrandom的范围：

00<=r<10

d<DoubleMax_Value是说d小于double类型数据的最大值

DoubleMAX_VALUE是java的double类里定义的

第一题

1

Face接口定义了counter属性，Test类继承Face接口,但Test类可以不实现Face接口的属性counter，但如果是方法，必须实现。所以Test的counter与Face的counter无关，本例中Test类中counter为静态，所以初始值默认为0，输出++counter-->1

第二题

2

int i=1; //i=1

int j=i++; //j=i=1 ,i++ -->i=2

if语句

(i>++j) //i=2,j先加1，在比较-->2>2-->false

所以if下语句(i += j;)不执行；

if语句用&&链接前后两部分,前者(i>++j)为false，并且是"与"关系，后面的为任何值，if语句都为false，所以if语句(i++ ==j)不执行，即：i=2,j=2