공부한 내용을 정리하는 글이라 틀린 내용이 있을 수 있습니다!
오늘 학습한 Buffered, byteStream, dataStream 대한 정리.
Buffered
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
public class BufferedTest {
public static void test() {
try {
String path =BufferedTest.class.getResource("").getPath();
System.out.println(path+"fkpz_o890_220609.jpg");
FileInputStream fis = new FileInputStream(path+"fkpz_o890_220609.jpg");
FileOutputStream fos = new FileOutputStream(path+"output1.jpg");
FileInputStream fis2 = new FileInputStream(path+"fkpz_o890_220609.jpg");
FileOutputStream fos2 = new FileOutputStream(path+"output1.jpg");
BufferedInputStream bis = new BufferedInputStream(fis2);
BufferedOutputStream bos = new BufferedOutputStream(fos2);
System.out.println(copy(fis,fos));
System.out.println(copy(bis, bos));
fis.close();
fos.close();
bis.close();
bos.close();
fis2.close();
fos2.close();
}catch(Exception e) {
e.printStackTrace();
}
}
private static long copy(InputStream is, OutputStream os) throws Exception {
long start = System.nanoTime();
while(true) {
int data = is.read();
if(data == -1)break; // -1 배열을 벗어나면 -1이뜸. ex) 배열 크기가 4인데 넘어가면 5로 넘어가면 -1취급 그래서 넘어가면 break!!!!
os.write(data);
}
long end = System.nanoTime();
return end - start;
}
}byteStream
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.InputStream;
import java.io.FileInputStream;
public class OutputStreamTest {
// 통신이랑 뭘까?
// - 데이터를 주고받는 것
// - 언제 통신한다고 얘기할 수 있을까?
// => 데이터를 보내고 답신을 받을 때? -> 어디로? 서버? 클라이언트? DB?
// => 위 내용은 일반적으로 생각할 수 있는 통신이다.
// => 키보드 입력 시 데이터가 메인보드를 통해 CPU에 전달된다.
public static void test() {
// C:\Users\KGA\git\Real\HomeWork2\Game\src\c230911\byteStream
String path = "C:/Users/KGA/git/Real/HomeWork2/Game/src/c230911/byteStream/test.db";
// Window 외 나머지(Linux, Unix, Mac, Ububtum Android, ...)
System.out.println();
try {
OutputStream os = new FileOutputStream(path); // 파일을 내보내는
os.write(10);
os.write(20);
os.write(30);
os.flush(); // 메모리가 가득 차지 않았어도 강제로 파일로 저장한다. HDD와 통신한다.
os.close();
InputStream is = new FileInputStream(path);
System.out.println(is.read());
System.out.println(is.read());
System.out.println(is.read());
System.out.println(is.read());
while(true) {
int data = is.read();
if(data == -1) break;
System.out.println("data : " + data);
}
is.close(); // 통신을 끝내라
}catch(Exception e) {
e.printStackTrace();
}
try {
OutputStream os = new FileOutputStream(path);
byte[] arr = {10, 20, 30};
os.write(arr);
os.flush();
os.close();
InputStream is = new FileInputStream(path);
byte[] arr1 = new byte[100]; //최대 몇 바이트까지 가져올지 배열로 생성한다.
int count = is.read(arr1);
for(int i = 0; i < count; i++) {
System.out.println("arr1[" + i + "] : " + arr1[i]);
}
// "가" << UTF-8 << 3byte << FF FF FF => AC 00 앞의 FF는 뭔지 알려주는것임.
}catch(Exception e){
e.printStackTrace();
}
}
}dataStream
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class DataStreamTest {
public static void test() {
try {
String path = DataStreamTest.class.getResource("").getPath() + "test.db";
FileOutputStream fos = new FileOutputStream(path);
DataOutputStream dos = new DataOutputStream(fos);
dos.writeInt(1); // 숫자를 넣을때
dos.writeUTF("강아지"); // 글자를 넣을때
dos.writeDouble(90.0);
dos.writeInt(2);
dos.writeUTF("고양이");
dos.writeDouble(93.0);
dos.writeInt(3);
dos.writeUTF("호랑이");
dos.writeDouble(100.0);
dos.flush(); // 파일에 저장
fos.close();
dos.close();
FileInputStream fis = new FileInputStream(path);
DataInputStream dis = new DataInputStream(fis);
for (int i = 0; i < 3; i++) {
int num = dis.readInt();
String name = dis.readUTF();
double score = dis.readDouble();
System.out.println(num + " ." + name + " : " + score + "점");
}
dis.close();
fis.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
ObjectStream
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
public class ObjectStreamTest {
public static void test() {
try {
String path = DataStreamTest.class.getResource("").getPath() + "test.db";
FileOutputStream fos = new FileOutputStream(path);
ObjectOutputStream oos = new ObjectOutputStream(fos);
Animal s1 = new Animal(1, "강아지", 90.0);
Animal s2 = new Animal(2, "고양이", 93.0);
Animal s3 = new Animal(3, "호랑이", 100.0);
oos.writeObject(s1);
oos.writeObject(s2);
oos.writeObject(s3);
oos.flush();
oos.close();
fos.close();
FileInputStream fis = new FileInputStream(path);
ObjectInputStream ois = new ObjectInputStream(fis);
Animal sr1 = (Animal) ois.readObject();
System.out.println(sr1.num);
System.out.println(sr1.name);
System.out.println(sr1.score);
sr1 = (Animal) ois.readObject();
System.out.println(sr1.num);
System.out.println(sr1.name);
System.out.println(sr1.score);
sr1 = (Animal) ois.readObject();
System.out.println(sr1.num);
System.out.println(sr1.name);
System.out.println(sr1.score);
ois.close();
fis.close();
// 데이터들끼리에 확실한 매칭을해주어야함. class한테 시리얼번호 붙여주는것.
} catch (Exception e) {
e.printStackTrace();
}
}
}
import java.io.Serializable;
public class Animal implements Serializable {
private static final long serialVersionUID = 1L; //자동으로 생성되는게 더 안전하게 만들어진다.
int num;
String name;
double score;
Animal(int num, String name, double score) {
this.num = num;
this.name = name;
this.score = score;
}
}
Path
import java.io.File;
import java.nio.file.Path;
import java.nio.file.Paths;
public class PathTest {
public static void test() {
// String path
Path path = Paths.get("src/c230911/../c230908");// 자동으로 잡아준다 / 나 \를
System.out.println(path.toAbsolutePath().normalize()); //toAbsolutePath 절대경로를 받아온다. normalize 경로 바꿔준다.
File file = new File(path.toString()+"\\Main2.java");
System.out.println(file.exists());
try {
// file.createNewFile();
file.mkdir();
}catch(Exception e) {
e.printStackTrace();
}
// exit
}
}Main 코드는
import c230911.buffered.BufferedTest;
import c230911.byteStream.OutputStreamTest;
import c230911.dataStream.DataStreamTest;
import c230911.dataStream.ObjectStreamTest;
import c230911.fileIo.FileIoTest;
import c230911.fileIo.SubTest;
public class Main {
public static void main(String[] args) {
OptionsTest.test();
MatchTest.test();
OutputStreamTest.test();
FileIoTest.test();
SubTest.test();
BufferedTest.test();
DataStreamTest.test();
ObjectStreamTest.test();
PathTest.test();
}
}
추가적인 내용
Match
import java.util.Arrays;
public class MatchTest {
public static void test() {
int[] arr = {1,3,5,7};
int[] arr1 = {2,4,6,8};
System.out.println(Arrays.stream(arr).allMatch(item ->item % 2 == 0)); //모든게 맞으면 true
System.out.println(Arrays.stream(arr1).allMatch(item ->item % 2 == 0));
System.out.println(Arrays.stream(arr).anyMatch(item ->item % 2 == 0)); //하나라도 맞으면 true
System.out.println(Arrays.stream(arr1).anyMatch(item ->item % 2 == 0));
System.out.println(Arrays.stream(arr).noneMatch(item ->item % 2 == 0)); //하나도 맞지않을때 true
System.out.println(Arrays.stream(arr1).noneMatch(item ->item % 2 == 0));
}예외 처리의 다양한 코드 작성방법
import java.util.Arrays;
import java.util.OptionalDouble;
public class OptionsTest {
public static void test() {
int[] arr = { 1, 3, 5, 7};
int[] arr1 = { 2, 4, 6, 8};
System.out.println(Arrays.stream(arr)
.filter(item->item%3==0).count());
System.out.println(Arrays.stream(arr1)
.filter(item->item%3==0).count());
System.out.println(Arrays.stream(arr).average());
System.out.println(Arrays.stream(arr1).average());
System.out.println(Arrays.stream(arr).average().getAsDouble());
System.out.println(Arrays.stream(arr1).average().getAsDouble());
System.out.println(Arrays.stream(arr).max().getAsInt());
System.out.println(Arrays.stream(arr1).max().getAsInt());
int[] arr2 = {};
try {
System.out.println(Arrays.stream(arr2).average()); // 1. try/catch (예외처리)
OptionalDouble od = Arrays.stream(arr2).average(); // 2. if/else (예외처리)
if(od.isPresent()) {
System.out.println(od.getAsDouble());
}
else {
System.out.println("없어");
}
System.out.println(Arrays.stream(arr).average().orElse(0.0)); // 3. orElse (예외처리)
System.out.println(Arrays.stream(arr2).average().orElse(0.0));
Arrays.stream(arr)
.average().
ifPresent(item->System.out.println("예외 : "+item)); // 4. ifPresent (예외처리)
Arrays.stream(arr2)
.average().
ifPresent(item->System.out.println("예외 : "+item));
System.out.println(Arrays.stream(arr)
.reduce(0, (a, b)->{
return a + b / 2 + 1;
}));
System.out.println(Arrays.stream(arr)
.reduce(0, (a, b)-> a + b / 2));
// 1, 3, 5, 7 => 16 / 2 => 8 + 4 => 12
// 0.5 int 0 / 1.5 int 1 / 2.5 int 2 / 3.5 int 3 => 0 + 1 + 2 + 3 + 4
}catch(Exception e) {
e.printStackTrace();
}
}
}
