Java 中异常处理的 9 个最佳实践

package com.zqf;
public class App
{
    public static void main(String[] args){
        System.out.println("First line");
        System.out.println("Second line");
        System.out.println("Third line");
        //初始化具有3个元素的素组
        int[] myIntArray = new int[]{1, 2, 3};
        print4thItemInArray(myIntArray);
        System.out.println("Fourth line");
        System.out.println("Fith line");
    }
    private static void print4thItemInArray(int[] arr) {
        //获取第4个(下标3)元素，因为没有所以抛出异常
        System.out.println(arr[3]);
        System.out.println("Fourth element successfully displayed!");
    }
}

package com.zqf;
public class App {
    public static void main(String[] args) {
        System.out.println("First line");
        System.out.println("Second line");
        System.out.println("Third line");
        //初始化具有3个元素的素组
        int[] myIntArray = new int[]{1, 2, 3};
        try {//捕捉异常
            print4thItemInArray(myIntArray);
        }catch (ArrayIndexOutOfBoundsException ex){//异常处理
            System.out.println("Have no four items!");
        }
        System.out.println("Fourth line");
        System.out.println("Fith line");
    }
    private static void print4thItemInArray(int[] arr) {
        //获取第4个(下标3)元素，因为没有所以抛出异常
        System.out.println(arr[3]);
        System.out.println("Fourth element successfully displayed!");
    }
}

public void doNotCloseResourceInTry() {
    FileInputStream inputStream = null;
    try {
        File file = new File("./tmp.txt");
        inputStream = new FileInputStream(file);
        // 使用inputStream读取文件
        // 不要这样做
        inputStream.close();
    } catch (FileNotFoundException e) {
        log.error(e);
    } catch (IOException e) {
        log.error(e);
    }
}

public void doNotCloseResourceInTry() {
    FileInputStream inputStream = null;
    try {
        File file = new File("./tmp.txt");
        inputStream = new FileInputStream(file);
        // 使用inputStream读取文件
    } catch (FileNotFoundException e) {
        log.error(e);
    } catch (IOException e) {
        log.error(e);
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (Exception e) {
                log.error(e);
            }
        }
    }
}

public void doNotCloseResourceInTry() {
    File file = new File("./tmp.txt");
    try (FileInputStream inputStream = new FileInputStream(file)) {
        // 使用inputStream读取文件
    } catch (FileNotFoundException e) {
        log.error(e);
    } catch (IOException e) {
        log.error(e);
    }
}

//不建议
public void doNotDoThis() throws Exception { ... }
//建议
public void doThis() throws NumberFormatException { ... }

/**
* This method does something extremely useful ...
*
* @param input
* @throws MyBusinessException if ... happens
*/
public void doSomething(String input) throws MyBusinessException { ... }

try {
  new Long("xyz");
} catch (NumberFormatException e) {
	log.error(e);
}

/**
 * Factory method for making a <code>NumberFormatException</code>
 * given the specified input which caused the error.
 *
 * @param   s   the input causing the error
 */
static NumberFormatException forInputString(String s) {
    return new NumberFormatException("For input string: \"" + s + "\"");
}

public void catchMostSpecificExceptionFirst() {
    try {
        doSomething("A message");
    } catch (NumberFormatException e) {
        log.error(e);
    } catch (IllegalArgumentException e) {
        log.error(e)
    }
}

//不要捕捉Throwable
public void doNotCatchThrowable() {
    try {
        // do something
    } catch (Throwable t) {
        // don't do this!
    }
}

public void doNotIgnoreExceptions() {
    try {
        // do something
    } catch (NumberFormatException e) {
        // this will never happen,I'm sure!!
    }
}

public void logAnException() {
    try {
        // do something
    } catch (NumberFormatException e) {
        log.error("This should never happen: " 
        	+ e + ",but I get a mistake!");
    }
}

try {
	new Long("xyz");
} catch (NumberFormatException e) {
	log.error(e);
	throw e;
}

17:44:28,945 ERROR TestExceptionHandling:65 - java.lang.NumberFormatException: For input string: "xyz"
Exception in thread "main" java.lang.NumberFormatException: For input string: "xyz"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Long.parseLong(Long.java:589)
	at java.lang.Long.(Long.java:965)
	at com.stackify.example.TestExceptionHandling.logAndThrowException(TestExceptionHandling.java:63)
	at com.stackify.example.TestExceptionHandling.main(TestExceptionHandling.java:58)

public void wrapException(String input) throws MyBusinessException {
	try {
		// do something
	} catch (NumberFormatException e) {
		throw new MyBusinessException("A message that describes the error.", e);
	}
}