18、IO流-标准流
1、标准输入输出流
System.in
System.out
2、转换流
InputStreamReader
OutputStreamWriter
3、字节缓冲流
4、字符缓冲流
/**
* System.in 方法1
*/
public static void startInput(){
String result = null;
BufferedReader bufferedReader = null;
try {
System.out.println("请输入字符 ");
bufferedReader = new BufferedReader(new InputStreamReader(System.in));
result = bufferedReader.readLine();
System.out.println(result);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* System.in 用法2
*/
public static void startInput2(){
byte []b = new byte[1024];
int count = 0;
try {
System.out.println("请输入字符 ");
count = System.in.read(b);
System.out.println(count);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* System.out 用法1
*/
public static void startOutput(){
try {
PrintStream printStream= new PrintStream("C:\\Users\\Administrator\\Desktop\\AAA.tet");
System.setOut(printStream);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* System.out 用法2
*/
public static void startOutput2(){
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(1024);
PrintStream printStream = new PrintStream(byteArrayOutputStream);
PrintStream systemPrintStream = System.out;//保存System.out
System.setOut(printStream);
String a = System.out.toString();
String b = printStream.toString();
String c = systemPrintStream.toString();
System.out.println("printStream " + printStream);
System.out.println("哈哈哈");
String infoString = byteArrayOutputStream.toString();
System.setOut(systemPrintStream);
System.out.println("infoString " + infoString);
System.out.println(a + " "+ b + " " + c);
}
/*
* System.out用法3
*/
public static void outPrintf2() {
// 定义一些变量，用来格式化输出。
double d = 345.678;
String s = "你好！";
int i = 1234;
// "%"表示进行格式化输出，"%"之后的内容为格式的定义。
System.out.printf("%f", d);// "f"表示格式化输出浮点数。
System.out.println();
System.out.printf("%9.2f", d);// "9.2"中的9表示输出的长度，2表示小数点后的位数。
System.out.println();
System.out.printf("%+9.2f", d);// "+"表示输出的数带正负号。
System.out.println();
System.out.printf("%-9.4f", d);// "-"表示输出的数左对齐（默认为右对齐）。
System.out.println();
System.out.printf("%+-9.3f", d);// "+-"表示输出的数带正负号且左对齐。
System.out.println();
System.out.printf("%d", i);// "d"表示输出十进制整数。
System.out.println();
System.out.printf("%o", i);// "o"表示输出八进制整数。
System.out.println();
System.out.printf("%x", i);// "x"表示输出十六进制整数。
System.out.println();
System.out.printf("%#x", i);// "x"表示输出带有十六进制标志的整数。
System.out.println();
System.out.printf("%s", s);// "s"表示输出字符串。
System.out.println();
System.out.printf("输出一个浮点数：%f，一个整数：%d，一个字符串：%s", d, i, s);
// 可以输出多个变量，注意顺序。
System.out.println();
System.out.printf("字符串：%2$s，%1$d的十六进制数：%1$#x", i, s);
// "X$"表示第几个变量。
}
附几种IO流文件读写方式（汉字不会读）
public class IOUtils {
/**
*1、 以字符流方式文件,输入流
* BufferedReader
* FileReader
*/
public static void readFileByBuffReadLine(File file) {
BufferedReader bufferedReader = null;
String tempString = "";
try {
bufferedReader = new BufferedReader(new FileReader(file));
boolean flag = false;
while((tempString = bufferedReader.readLine()) != null){//读入的数据不为空
String []tempsStrings = tempString.split(" ");//剪切存储数组
if (tempsStrings[0].matches("\\d{3}")) { //判断该字符串是否满足三个数字
System.out.println(tempsStrings[0]);
System.out.println(tempsStrings[1]);
flag = true;
}else if (flag) {
System.out.println(tempString.trim());//忽略空格输出
}
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO: handle exception
}finally{
try {
bufferedReader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
*1、以字符流读取文件，按字符读取
* InputStreamReader
* FileInputStream
*/
public static void readFileByStreamReader(File file){
Reader reader = null;
try {
reader = new InputStreamReader(new FileInputStream(file));
int tempChar;
String tempString = "";
boolean flag = false;
while((tempChar = reader.read()) != -1){//reader.reader()读入数据对应ASCII表 的int值 ，当读入不空
if ((char)tempChar != '\n') {
tempString += String.valueOf((char)tempChar);
}else{
String []tempsStrings = tempString.split(" ");//剪切存储数组
if (tempsStrings[0].matches("\\d{3}")) { //判断该字符串是否满足三个数字
flag = true;
System.out.println(tempsStrings[0]);
if (tempsStrings.length == 3) {
System.out.println(tempsStrings[1]);
}else {
System.out.print(tempsStrings[1]);
}
}else {
if (flag) {
System.out.println(tempString.trim());//忽略空格输出
}
}
// System.out.println("读入的数据"+ tempString);
// System.out.print(tempString);
tempString = "";
}
// System.out.print((char)tempChar);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (IOException e) {
// TODO: handle exception
}finally{
try {
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
*3、 以字节为单位读取文件
* FileInputStream
*/
public static void readByFileInputStream(File file){
InputStream inputStream = null;
byte[] tempbyte = new byte[1024];
int i = 0;
int byteRead = 0;
try {
inputStream = new FileInputStream(file);
while((byteRead = inputStream.read(tempbyte)) != -1){//read()传参数表示读的是个数，不传读的是对应的ASC码表
System.out.println("每次读的字节数 "+ byteRead);
System.out.println(new String(tempbyte, 0, byteRead));
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
*4、 以文件字节流方式写入内容
* FileOutputStream
*/
public static void writeFileOutPutStream(File file, String content){
FileOutputStream fileOutputStream = null;
try {
fileOutputStream = new FileOutputStream(file);
byte[] tempBytes = content.getBytes();//字符串转字节数组
fileOutputStream.write(tempBytes);//写入流
fileOutputStream.flush();//从流写入.txt文件
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
if (fileOutputStream != null) {
try {
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
*5、 以字符流的方式写入文件
* BufferedWriter
* PrintWriter
*/
public static void writerByBufferWriter(File file, String contents){
BufferedWriter bufferedWriter = null;
try {
bufferedWriter = new BufferedWriter(new PrintWriter(file));
bufferedWriter.write(contents);
bufferedWriter.flush();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if (bufferedWriter != null) {
try {
bufferedWriter.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
/**
*6、 以字符流的方式写入文件//可追加文件
* BuffereWriter
* FileWriter
*/
public static void writerByBufferWriterAdd(File file, String contents){
BufferedWriter bufferedWriter = null;
try {
bufferedWriter = new BufferedWriter(new FileWriter(file, true));
bufferedWriter.write(contents);
bufferedWriter.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if (bufferedWriter != null) {
try {
bufferedWriter.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}