νμ΅ λ΄μ©
- Exception : μμΈ != error
public class Mainclass {
public static void main(String[] args) {
int c;
try {
c = 4 / 0; //tryλ¬Έμμ μμΈκ° λ°μνλ©΄
}catch(ArithmeticException e) {
c = -1; //catchλ¬Έμ΄ μνλλ€.
}
System.out.println(c);
}
} //κ²°κ³Ό κ° : -1
- 2μ§ ν¨μ μ§μ λ§λ€κΈ°
μμ binary λ©μλλ λ΄κ° λ§λ€μκ³ , μλ change λ©μλλ κ°μ¬λμ΄ λ§λ€μ΄μ£Όμ ¨λ€.
λ΄κ° λ§λ κ²λ μ μ μλμ λμμ§λ§, μλ λ©μλμ λΉκ΅ν΄λ³΄λ λ κ°λ¨νκ² λνλΌ μ μλ λ°©λ²μ μκ² λμλ€.
package work02;
public class MainClass {
public static void main(String[] args) {
int number = 75;
System.out.println(change(number));
}
static String binary (int number) {
String binary = "";
while(true) {
if(number % 2 == 1 && number != 1) {
number /= 2;
binary = "1"+ binary;
}
else if(number % 2 == 0 && number != 0) {
number /= 2;
binary = "0"+ binary;
}
else if(number == 1) {
binary = "1"+ binary;
break;
}
else if(number == 0) {
binary = "0"+ binary;
break;
}
}
return binary;
}
static String change(int number10) {
String number2 = "";
int tag; //λλ¨Έμ§κ°(0,1)μ ꡬνλ μ μ
while(true) {
tag = number10 % 2;
number2 = tag + number2;
if (number10 / 2 == 0) { //λ¨μμκ° 1μ΄λλ©΄ 1/2 = 0μ΄λλ€.
break;
}
number10 = number10/2;
}
return number2;
}
}
- File ν΄λμ€
File ν΄λμ€λ₯Ό νμ©ν κΈ°λ₯, λ©μλλ₯Ό 곡λΆνλ€. μ£Όλ‘ μ 보λ₯Ό κ°μ Έμ€κ±°λ νμΌ, ν΄λ μμ±μΌλ‘ λ§μ΄ μ΄λ€.
package fileIO;
import java.io.File;
import java.io.IOException;
public class MainClass {
public static void main(String[] args) {
/*
file : μ μ₯ 맀체 == κΈ°λ₯
Database(file)
*.txt -> 2μ§μ lib (μ μ )
Dynamic Link Library(dll) (λμ )
*/
File file = new File("c:\\"); //File ν΄λμ€ νμ©νλ€.
// νμΌ μ‘°μ¬ (νμ¬ cλλΌμ΄λΈμ μλ νμΌ λ¦¬μ€νΈκ° λμ΄)
/*
String filelist[] = file.list();
for (int i = 0; i < filelist.length; i++) {
System.out.println(filelist[i]);
}
*/
//νμΌλͺ
κ³Ό ν΄λλͺ
μ μ‘°μ¬ ( isFile() -> νμΌμ 보μ¬μ€. isDirectory() -> ν΄λλ₯Ό 보μ¬μ€ )
File filelist[] = file.listFiles();
/*
for (int i = 0; i < filelist.length; i++) {
if(filelist[i].isFile()) {
System.out.println("[νμΌ]" + filelist[i].getName());
}
else if(filelist[i].isDirectory()) {
System.out.println("[ν΄λ]" + filelist[i].getName());
}
else {
System.out.println("[?]" + filelist[i].getName());
}
}
*/
//νμΌ ν¬μΈν° μμ± (λ΄μ©μ μμ±νμ§ μκ³ νμΌ μμ²΄λ§ μμ±)
File newFile = new File("F:\\tmp\\newfile.txt");
try {
if(newFile.createNewFile()) { //boolean createNewFile() -> μ£Όμ΄μ§ μ΄λ¦μ νμΌμ΄ μμΌλ©΄ μλ‘ μμ±
System.out.println("νμΌ μμ± μ±κ³΅");
}else {
System.out.println("νμΌ μμ± μ€ν¨");
}
}catch(IOException e) {
e.printStackTrace();
}
// ν΄λ μμ±
File newDir = new File("F:\\tmp1\\sub");
if(newDir.mkdirs()) { // boolean mkdir() ->ν΄λΉ κ²½λ‘μ ν΄λλ₯Ό λ§λ λ€.
// boolean mkdirs() -> μ‘΄μ¬νμ§ μλ λΆλͺ¨ν΄λκΉμ§ ν¬ν¨νμ¬ λ§λ λ€.
System.out.println("ν΄λ μμ± μ±κ³΅");
} else {
System.out.println("ν΄λ μμ± μ€ν¨");
}
// file μ‘΄μ¬ μ¬λΆ
if(newFile.exists()) { // boolean exists() -> μ‘΄μ¬μ¬λΆ λ¦¬ν΄ λ©μλ
System.out.println("newFile.txtκ° μ‘΄μ¬ν©λλ€");
} else {
System.out.println("newFile.txtκ° μ‘΄μ¬νμ§ μμ΅λλ€");
}
//μ½κΈ° μ μ©μΌλ‘ λ§λ€κΈ°
newFile.setReadOnly();
// μ°κΈ° κ°λ₯ μ¬λΆ (μ μ½κΈ° μ μ©μΌλ‘ λ§λ€λ©΄ μ°κΈ°κ° λΆκ°λ₯ν΄μ§)
if(newFile.canWrite()) { //boolean canWrite() -> μΈμ μλμ§ μ¬λΆλ₯Ό 리ν΄
System.out.println("μ΄ νμΌμ μ°κΈ°κ° κ°λ₯ν©λλ€.");
} else {
System.out.println("μ΄ νμΌμ μ°κΈ°λ₯Ό ν μ μμ΅λλ€.");
}
//μμ
newFile.delete(); //boolean delete() -> νμΌμ΄λ ν΄λ μμ . λ¨, ν΄λλ λΉμ΄μμ§ μμΌλ©΄ μμ λΆκ°
}
}
- FileWriter ν΄λμ€
νμΌ μ°κΈ°μ νμν ν΄λμ€. FileWriterμ BufferedWriter μ΄μ© κ°λ₯νλ€.
package fileWrite;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
public class MainClass {
public static void main(String[] args) {
//νμΌ μ°κΈ°
File file = new File("F:\\tmp\\newfile.txt");
try {
//κΈ°λ³Έ νμΌ μ°κΈ° λ°©λ². FileWriter ν΄λμ€ νμ©νλ€.
/*
FileWriter fwriter = new FileWriter(file);
fwriter.write("μλ
νμΈμ");
fwriter.write("hello");
fwriter.close();
*/
//μΆκ° μ°κΈ°
/*
FileWriter fwriter = new FileWriter(file, true); //FileWriter μλ κ³³μ true λ£μ΄μ£Όλ©΄ μΆκ°μ°κΈ°
//λλ²μ§Έ boolean μ
λ ₯ νλΌλ―Έν°λ νμΌμ μΆκ°λͺ¨λ(append)λ‘ μ΄κ²μΈμ§μ λν ꡬλΆκ°μ΄λ€.
//νμΌμ μΆκ°λͺ¨λλ‘ μ΄λ©΄ κΈ°μ‘΄νμΌμ λ΄μ©μ΄νλΆν° νμΌμ΄ μ°μ¬μ§κ² λλ€.
fwriter.write("λ°κ°μ΅λλ€");
fwriter.close();
*/
//**BufferedWriter**λ₯Ό νμ©ν μ°κΈ° (λ§μ΄ μ¬μ©)
/*
FileWriter fwriter = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fwriter);
PrintWriter pw = new PrintWriter(bw);
*/ //μμ 3μ€μ μλ νμ€λ‘ ννμ΄ κ°λ₯νλ€.
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(file)));
//FileWriter μλ κ³³μ true λ£μ΄μ£Όλ©΄ μΆκ°μ°κΈ°
pw.println("μλ
νμΈμ");
pw.print("hello");
pw.println("world");
pw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
- FileReader ν΄λμ€
νμΌ μ½κΈ°λ₯Ό μν ν΄λμ€. νκΈμμ© νμΌμμ μ½μ΄μ€κΈ° λλ¬Έμ λ¬Έμ₯μΌλ‘ μ½μ΄μ€λ BufferedReaderκ° λ μμ£Ό μ°μΈλ€.
package fileRead;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
public class MainClass {
public static void main(String[] args) {
// νμΌ μ½κΈ°
File file = new File("F:\\tmp\\newfile.txt");
try {
// νκΈμμ© νμΌμμ μ½κΈ°. FileReader ν΄λμ€. --> ν¨μ¨μ μ΄μ§ λͺ»ν΄μ μ μ¬μ©μ μν¨.
/*
FileReader fr = new FileReader(file);
int ch = fr.read();
while(ch != -1) { //EOF -> End Of File
System.out.print((char)ch);
ch = fr.read();
}
fr.close();
*/
// λ¬Έμ₯μΌλ‘ μ½κΈ° (BufferedReaderλ₯Ό νμ©ν μ½κΈ° λ°©λ². μ μΌ λ§μ΄ νμ©ν¨.)
BufferedReader br = new BufferedReader(new FileReader(file));
String str;
while((str = br.readLine()) != null) {
System.out.println(str);
}
br.close();
} catch (FileNotFoundException e) { // νμΌμ΄ μμμλ μμΌλ μ΅μ
μ
μ΄ κ±Έλ¦Ό
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) { // μ΅μ
μ
μ μ¬λ¬κ° μ°μ§μκ³ 'catch (Exception e)' νλλ§ μ¨μ€λ λκ°λ€.
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
'π» κ°λ° > π TIL (Today I Learned)' μΉ΄ν κ³ λ¦¬μ λ€λ₯Έ κΈ
21.01.30 TIL (JAVA flnal, static, μΆμ ν΄λμ€, μΈν°νμ΄μ€) (0) | 2021.01.31 |
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21.01.27 TIL (D+13 JAVA μμ±μ, μμ, μλμ±) (0) | 2021.01.27 |
21.01.22 TIL (D+10 JAVA μΊλ¦°λ, μ£Όμλ‘ λ§λ€κΈ°) (0) | 2021.01.22 |
21.01.21 TIL (D+9 JAVA sorting, λ©μλ) (0) | 2021.01.21 |
21.01.18 TIL(D+6 JAVA λ°λ³΅λ¬Έ) (0) | 2021.01.18 |