1. 本周学习总结
1.1 以你喜欢的方式(思维导图或其他)归纳总结异常相关内容。
2. 书面作业
本次PTA作业题集异常
1.常用异常
题目5-1
1.1 截图你的提交结果(出现学号)
1.2 自己以前编写的代码中经常出现什么异常、需要捕获吗(为什么)?应如何避免?
1.3 什么样的异常要求用户一定要使用捕获处理?
2.处理异常使你的程序更加健壮
题目5-2
2.1 截图你的提交结果(出现学号)
2.2 实验总结
3.throw与throws
题目5-3
3.1 截图你的提交结果(出现学号)
3.2 阅读Integer.parsetInt源代码,结合3.1说说抛出异常时需要传递给调用者一些什么信息?
源代码
public static int parseInt(String s, int radix) throws NumberFormatException { /* * WARNING: This method may be invoked early during VM initialization * before IntegerCache is initialized. Care must be taken to not use * the valueOf method. */ if (s == null) { throw new NumberFormatException("null"); } if (radix < Character.MIN_RADIX) { throw new NumberFormatException("radix " + radix + " less than Character.MIN_RADIX"); } if (radix > Character.MAX_RADIX) { throw new NumberFormatException("radix " + radix + " greater than Character.MAX_RADIX"); } int result = 0; boolean negative = false; int i = 0, len = s.length(); int limit = -Integer.MAX_VALUE; int multmin; int digit; if (len > 0) { char firstChar = s.charAt(0); if (firstChar < '0') { // Possible leading "+" or "-" if (firstChar == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (firstChar != '+') throw NumberFormatException.forInputString(s); if (len == 1) // Cannot have lone "+" or "-" throw NumberFormatException.forInputString(s); i++; } multmin = limit / radix; while (i < len) { // Accumulating negatively avoids surprises near MAX_VALUE digit = Character.digit(s.charAt(i++),radix); if (digit < 0) { throw NumberFormatException.forInputString(s); } if (result < multmin) { throw NumberFormatException.forInputString(s); } result *= radix; if (result < limit + digit) { throw NumberFormatException.forInputString(s); } result -= digit; } } else { throw NumberFormatException.forInputString(s); } return negative ? result : -result; } /** * Parses the string argument as a signed decimal integer. The * characters in the string must all be decimal digits, except * that the first character may be an ASCII minus sign {@code '-'} * ({@code '\u005Cu002D'}) to indicate a negative value or an * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to * indicate a positive value. The resulting integer value is * returned, exactly as if the argument and the radix 10 were * given as arguments to the {@link #parseInt(java.lang.String, * int)} method. * * @param s a {@code String} containing the {@code int} * representation to be parsed * @return the integer value represented by the argument in decimal. * @exception NumberFormatException if the string does not contain a * parsable integer. */ public static int parseInt(String s) throws NumberFormatException { return parseInt(s,10); }
4.函数题
题目4-1(多种异常的捕获)
3.1 截图你的提交结果(出现学号)
3.2 一个try块中如果可能抛出多种异常,捕获时需要注意些什么?
5.为如下代码加上异常处理
byte[] content = null;
FileInputStream fis = new FileInputStream("testfis.txt"); int bytesAvailabe = fis.available();//获得该文件可用的字节数 if(bytesAvailabe>0){ content = new byte[bytesAvailabe];//创建可容纳文件大小的数组 fis.read(content);//将文件内容读入数组 } System.out.println(Arrays.toString(content));//打印数组内容5.1 改正代码,让其可正常运行。注1:里面有多个方法均可能抛出异常。注2:要使用finally关闭资源。
5.2 使用Java7中的try-with-resources来改写上述代码实现自动关闭资源.
3. 码云上代码提交记录
题目集:异常
3.1. 码云代码提交记录
在码云的项目中,依次选择“统计-Commits历史-设置时间段”, 然后搜索并截图