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 <a href="/m/category/dev%20book/Effective%20Java">dev book/Effective Java</a><h2>[아이템9] try-finally 보다는 try-with-resources를 사용하라</h2>
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 네로 neroya
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 <time>2021. 9. 27. 20:11</time>
 
 
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 <h2 data-ke-size="size26"># try-finally 보다는 try-with-resources를 사용하라</h2>
##&nbsp;1.&nbsp;자원이&nbsp;닫힘을&nbsp;보장하는&nbsp;수단,&nbsp;try-finally의&nbsp;단점
-&nbsp;코드&nbsp;가독성에&nbsp;있어&nbsp;지저분하다.
-&nbsp;두번째&nbsp;예외가&nbsp;첫번째&nbsp;예외를&nbsp;집어삼켜버러&nbsp;실제&nbsp;시스템에서&nbsp;디버깅을&nbsp;어렵게한다.
<pre id="code_1632643950824" data-ke-language="java" data-ke-type="codeblock"><code>static void copy(String src, String dst) throws IOException {
 InputStream in = new FileInputStream(src);
 try {
 OutStream out = new FileOutStream(dst);
 try {
 byte[] buf = new byte[BUFFER_SIZE];
 int n;
 while((n = in.read(buf)) &gt;= 0) 
 out.write(buf, 0, n);
 }finally {
 out.close();
 }
 }finally {
 in.close();
 }
}</code></pre>


##&nbsp;2.&nbsp;자원&nbsp;회수의&nbsp;최선책&nbsp;try-with-resources
-&nbsp;AutoCloseable&nbsp;인터페이스&nbsp;구현:&nbsp;close()&nbsp;메서드&nbsp;하나만&nbsp;정의
<pre id="code_1632643967964" data-ke-language="java" data-ke-type="codeblock"><code>public interface AutoCloseable {
 void close() throws Exception;
}</code></pre>
<pre id="code_1632643986504" data-ke-language="java" data-ke-type="codeblock"><code>static void copy(String src, String dst) throws IOException {
 try (InputStream in = new FileInputStream(src);
 OutStream out = new FileOutStream(dst)) {
 byte[] buf = new byte[BUFFER_SIZE];
 int n;
 while((n = in.read(buf)) &gt;= 0) 
 out.write(buf, 0, n);
 } catch (IOException e) {
 return defaultValue;
 }
}</code></pre>
-&nbsp;읽기&nbsp;쉽고&nbsp;문제&nbsp;진단에&nbsp;유리하다.
-&nbsp;catch를&nbsp;이용해&nbsp;try문을&nbsp;중첩하지&nbsp;않고도&nbsp;다수의&nbsp;예외&nbsp;처리가&nbsp;가능하다.
-&nbsp;숨겨진&nbsp;예외도&nbsp;버려지지&nbsp;않고,&nbsp;suppressed&nbsp;꼬리표를&nbsp;달고&nbsp;출력된다.

readLine()과&nbsp;close()&nbsp;호출&nbsp;양쪽에서&nbsp;예외가&nbsp;발생하면,&nbsp;close()&nbsp;예외는&nbsp;숨겨지고&nbsp;readLine()에서&nbsp;발생한&nbsp;예외가&nbsp;기록된다.&nbsp;&nbsp;

 
 
					
 
 
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 </div></div>

개구린개구리

# try-finally 보다는 try-with-resources를 사용하라
## 1. 자원이 닫힘을 보장하는 수단, try-finally의 단점
- 코드 가독성에 있어 지저분하다.
- 두번째 예외가 첫번째 예외를 집어삼켜버러 실제 시스템에서 디버깅을 어렵게한다.
static void copy(String src, String dst) throws IOException {
    InputStream in = new FileInputStream(src);
    try {
        OutStream out = new FileOutStream(dst);
        try {
            byte[] buf = new byte[BUFFER_SIZE];
            int n;
            while((n = in.read(buf)) >= 0) 
                out.write(buf, 0, n);
        }finally {
            out.close();
        }
    }finally {
        in.close();
    }
}
 
 
## 2. 자원 회수의 최선책 try-with-resources
- AutoCloseable 인터페이스 구현: close() 메서드 하나만 정의
public interface AutoCloseable {
    void close() throws Exception;
}
static void copy(String src, String dst) throws IOException {
    try (InputStream in = new FileInputStream(src);
        OutStream out = new FileOutStream(dst)) {
            byte[] buf = new byte[BUFFER_SIZE];
            int n;
            while((n = in.read(buf)) >= 0) 
                out.write(buf, 0, n);
    } catch (IOException e) {
        return defaultValue;
    }
}
- 읽기 쉽고 문제 진단에 유리하다.
- catch를 이용해 try문을 중첩하지 않고도 다수의 예외 처리가 가능하다.
- 숨겨진 예외도 버려지지 않고, suppressed 꼬리표를 달고 출력된다.
 
readLine()과 close() 호출 양쪽에서 예외가 발생하면, close() 예외는 숨겨지고 readLine()에서 발생한 예외가 기록된다.

[아이템9] try-finally 보다는 try-with-resources를 사용하라

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