Java中的异常处理 #yyds干货盘点#

1、类关系图

2、try-catch-finally

语法：

try{
	执行过程中可能出现错误的代码
} catch(可能出现的异常类型1 ){
   异常处理方案
} catch(可能出现的异常类型2 ){
   异常处理方案
} catch(可能出现的异常类型3 ){
   异常处理方案
} finally {
   无论是否发生异常都会执行的代码
}

示例1：

public static void main(String[] args) {
    try {
        System.out.println(3/0);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        System.out.println("finally");
    }
}

• 结果：

示例2：

 public static void main(String[] args) {
    File file = new File("pom.xml");
    FileReader reader = null;
    try {
        reader = new FileReader(file);
        char[] buf = new char[128];
        int len = -1;
        while ((len = reader.read(buf)) != -1) {
            String res = new String(buf, 0, len);
            System.out.println(res);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

3、Multi-catch

语法：

try{
	执行过程中可能出现错误的代码
} catch(可能出现的异常类型1 |可能出现的异常类型2 |可能出现的异常类型3 …){
   异常处理方案
} 

示例：

public static void main(String[] args) {
    int d = new Scanner(System.in).nextInt();
    try {
        System.out.println(3 / d);
        new File("G:/dd/aa/ab.txt").createNewFile();
    } catch (ArithmeticException e) {
        e.printStackTrace();
    } catch (IOException e) {
        // System.out.println(e.getMessage());
        e.printStackTrace();
    }
    //可以简写为
    try {
        System.out.println(3 / d);
        new File("G:/dd/aa/ab.txt").createNewFile();
    } catch (ArithmeticException | IOException e) {
        e.printStackTrace();
    }
}

4、try-with-resources

语法：

Try(待释放的资源的创建语句){ //创建资源时可能会抛出异常
	执行过程中可能出现错误的代码
} catch(可能出现的异常类型1 |可能出现的异常类型2 |可能出现的异常类型3 …){
   异常处理方案
} 

示例1： 系统会自动释放资源

 public static void main(String[] args) {
    File file = new File("pom.xml");
    try (FileReader reader = new FileReader(file);) {
        char[] buf = new char[128];
        int len = -1;
        while ((len = reader.read(buf)) != -1) {
            String res = new String(buf, 0, len);
            System.out.println(res);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

示例2：

public static void main(String[] args) {
	try (FileReader reader = new FileReader(new File("E:/data.txt"));
			FileWriter writer = new FileWriter(new File("E:/abc.txt"));) {
		char[] buf = new char[16];
		int len = -1;
		while ((len = reader.read(buf)) != -1) {
			String str = new String(buf, 0, len);
			writer.write(str);
		}
	} catch (Exception e) {
		System.out.println("cuo le");
	}
}

5、抛出异常

示例1：

 public static void main(String[] args) throws IOException {
        File file = new File("pom.xml");
        FileReader reader = new FileReader(file);
        char[] buf = new char[128];
        int len = -1;
        while((len = reader.read(buf))!= -1){
            String res = new String(buf, 0, len);
            System.out.println(res);
        }
        reader.close();
    }

示例2:

 public static void main(String[] args) throws IOException {
	FileReader reader = new FileReader(new File("E:/data.txt"));
	char[] buf = new char[16];
	int len = -1;
	while((len = reader.read(buf)) != -1) {
		String str = new String(buf,0,len);
		System.out.println(str);
	}
	reader.close();
}

示例3:

 public static void main(String[] args) throws IOException {
	FileReader reader = new FileReader(new File("E:/data.txt"));
	FileWriter writer = new FileWriter(new File("E:/abc.txt"));
	char[] buf = new char[16];
	int len = -1;
	while ((len = reader.read(buf)) != -1) {
		String str = new String(buf, 0, len);
		writer.write(str);
	}
	if (reader != null) {
		reader.close();
	}
	if (writer != null) {
		writer.close();
	}
}