feat: add java exception

niumoo · niumoo · commit aee250d8c70e · 2023-04-28T16:20:55.000+08:00
diff --git a/README.md b/README.md
@@ -49,6 +49,7 @@
 - [Java 多态](https://www.wdbyte.com/java/polymorphism/)
 - [Java Scanner](https://www.wdbyte.com/java/scanner/)
 - [Java 日期时间 Date](https://www.wdbyte.com/java/date/)
+- [Java 异常处理](https://www.wdbyte.com/java/exception/)
 
 ## 🌿 SpringBoot 2.x 教程
 
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException1.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException1.java
@@ -0,0 +1,12 @@
+package com.wdbyte.exception;
+
+/**
+ * @author niulang
+ */
+public class JavaException1 {
+
+    public static void main(String[] args) {
+        String str = null;
+        System.out.println(str.length());
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException2.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException2.java
@@ -0,0 +1,13 @@
+package com.wdbyte.exception;
+
+/**
+ * @author niulang
+ */
+public class JavaException2 {
+
+    public static void main(String[] args) {
+        String[] strArr = {"www", "wdbyte", "com"};
+        System.out.println(strArr[0]);
+        System.out.println(strArr[3]);
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException3.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException3.java
@@ -0,0 +1,19 @@
+package com.wdbyte.exception;
+
+/**
+ * @author niulang
+ */
+public class JavaException3 {
+
+    public static void main(String[] args) {
+        String[] strArr = {"www", "wdbyte", "com"};
+        try {
+            System.out.println(strArr[0]);
+            System.out.println(strArr[3]);
+        } catch (ArrayIndexOutOfBoundsException e) {
+            System.out.println("发生数组访问越界异常，不能访问超过数组长度的元素，数组长度为:" + strArr.length);
+            System.out.println("异常描述:" + e.getMessage());
+            e.printStackTrace();
+        }
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException4.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException4.java
@@ -0,0 +1,19 @@
+package com.wdbyte.exception;
+
+/**
+ * @author niulang
+ */
+public class JavaException4 {
+
+    public static void main(String[] args) {
+        String[] strArr = {"www", "wdbyte", "com"};
+        try {
+            System.out.println(strArr[0]);
+            System.out.println(strArr[3]);
+        } catch (ArrayIndexOutOfBoundsException e) {
+            //throw e;
+            throw new RuntimeException(e);
+        }
+        System.out.println("执行完成。");
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException5.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException5.java
@@ -0,0 +1,35 @@
+package com.wdbyte.exception;
+
+import org.apache.commons.lang3.ObjectUtils.Null;
+
+/**
+ * @author niulang
+ */
+public class JavaException5 {
+
+    public static void main(String[] args) {
+        String[] strArr = {"www", null, "com"};
+        try {
+            System.out.println(strArr[0].length());
+            // 空指针异常
+            System.out.println(strArr[1].length());
+            System.out.println(strArr[3].length());
+        } catch (ArrayIndexOutOfBoundsException e) {
+            System.out.println("发生数组访问越界异常，不能访问超过数组长度的元素，数组长度为:" + strArr.length);
+        } catch (NullPointerException e) {
+            System.out.println("发现空指针异常");
+        }
+        System.out.println("执行完成。");
+
+        try {
+            System.out.println(strArr[0].length());
+            // 空指针异常
+            System.out.println(strArr[1].length());
+            // 越界异常
+            System.out.println(strArr[3].length());
+        } catch (Exception e) {
+            System.out.println("发生异常：" + e.getMessage());
+            e.printStackTrace();
+        }
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException6.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException6.java
@@ -0,0 +1,20 @@
+package com.wdbyte.exception;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+/**
+ * @author niulang
+ * @date 2023/04/27
+ */
+public class JavaException6 {
+
+    public static void main(String[] args) {
+        try {
+            Files.readAllLines(Paths.get("c:/abc.txt"));
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException7.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException7.java
@@ -0,0 +1,22 @@
+package com.wdbyte.exception;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+/**
+ * @author niulang
+ * @date 2023/04/27
+ */
+public class JavaException7 {
+
+    public static void main(String[] args) {
+        try {
+            Files.readAllLines(Paths.get("c:/abc.txt"));
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+
+        }
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException8.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/JavaException8.java
@@ -0,0 +1,33 @@
+package com.wdbyte.exception;
+
+/**
+ * @author niulang
+ */
+public class JavaException8 {
+
+    public static void main(String[] args) {
+        int result = 0;
+        try {
+            result = calc(4, 2);
+            System.out.println("4 / 2 = " + result);
+        } catch (MyException e) { // 不处理异常会报错
+            e.printStackTrace();
+        }
+
+        try {
+            result = calc(4, 0);
+            System.out.println("4 / 0 = " + result);
+        } catch (MyException e) { // 不处理异常会报错
+            e.printStackTrace();
+        }
+    }
+
+    public static int calc(int a, int b) throws MyException {
+        if (b == 0) {
+            throw new MyException("除数不能为0");
+        }
+        return a / b;
+    }
+}
+
+
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/MyException.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/MyException.java
@@ -0,0 +1,7 @@
+package com.wdbyte.exception;
+
+public class MyException extends Exception {
+    public MyException(String message) {
+    super(message); 
+  }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/ReadFile.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/ReadFile.java
@@ -0,0 +1,45 @@
+package com.wdbyte.exception;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class ReadFile {
+
+    public static void main(String[] args) {
+
+        File file = new File("pom2.xml");
+        FileReader fileReader = null;
+        BufferedReader bufferedReader = null;
+        try {
+            fileReader = new FileReader(file);
+            bufferedReader = new BufferedReader(fileReader);
+            String line;
+            while ((line = bufferedReader.readLine()) != null) {
+                System.out.println(line);
+            }
+            bufferedReader.close();
+            fileReader.close();
+        } catch (FileNotFoundException e) {
+            System.out.println("文件不存在");
+        } catch (IOException e) {
+            System.out.println("读取文件失败");
+        } finally {
+            try {
+                System.out.println("开始关闭资源");
+                if (bufferedReader != null) {
+                    bufferedReader.close();
+                    System.out.println("关闭 bufferedReader");
+                }
+                if (fileReader != null) {
+                    fileReader.close();
+                    System.out.println("关闭 fileReader");
+                }
+            } catch (IOException e) {
+                System.out.println("关闭文件失败");
+            }
+        }
+    }
+}
diff --git a/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/ReadFile2.java b/core-java-modules/core-java-base/src/main/java/com/wdbyte/exception/ReadFile2.java
@@ -0,0 +1,25 @@
+package com.wdbyte.exception;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class ReadFile2 {
+
+    public static void main(String[] args) {
+        File file = new File("pom.xml");
+        try (FileReader fileReader = new FileReader(file); BufferedReader bufferedReader = new BufferedReader(
+            fileReader);) {
+            String line;
+            while ((line = bufferedReader.readLine()) != null) {
+                System.out.println(line);
+            }
+        } catch (FileNotFoundException e) {
+            System.out.println("文件不存在");
+        } catch (IOException e) {
+            System.out.println("读取文件失败");
+        }
+    }
+}
