public class Calculator
 {
  public int devide(int num1,
int num2)
 {
    //判断除数是否为0
    if(num2
 == 0)
 {
      throw new IllegalArgumentException("除数不能为零");
    }
     
    return num1/num2;
  }
}

public static void testException1()
 {
    int[]
 ints = new int[]
 { 1,
2,
3,
4 };
    System.out.println("异常出现前");
    try {
      System.out.println(ints[4]);
      System.out.println("我还有幸执行到吗");//
 发生异常以后，后面的代码不能被执行
    }
catch (IndexOutOfBoundsException
 e) {
      System.out.println("数组越界错误");
    }
    System.out.println("异常出现后");
  }
  /*output:
  异常出现前
  数组越界错误
  4
  异常出现后
  */

public static void testException2()
 {
    int[]
 ints = new int[]
 { 1,
2,
3,
4 };
    System.out.println("异常出现前");
    System.out.println(ints[4]);
    System.out.println("我还有幸执行到吗");//
 发生异常以后，他后面的代码不能被执行
  }

public class Rethrow
 {
  public static void readFile(String
 file) throws FileNotFoundException
 {
    try {
      BufferedInputStream
 in = new BufferedInputStream(new FileInputStream(file));
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
      System.err.println("不知道如何处理该异常或者根本不想处理它，但是不做处理又不合适，这是重新抛出异常交给上一级处理");
      //重新抛出异常
      throw e;
    }
  }
   
  public static void printFile(String
 file) {
    try {
      readFile(file);
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
    }
  }
   
  public static void main(String[]
 args) {
    printFile("D:/file");
  }
}
 

public class ExceptionA
extends Exception
 {
  public ExceptionA(String
 str) {
    super();
  }
}
 
public class ExceptionB
extends ExceptionA
 {
 
  public ExceptionB(String
 str) {
    super(str);
  }
}
 
public class ExceptionC
extends ExceptionA
 {
  public ExceptionC(String
 str) {
    super(str);
  }
}

public class NeverCaught
 {
  static void f()
throws ExceptionB{
    throw new ExceptionB("exception
 b");
  }
 
  static void g()
throws ExceptionC
 {
    try {
      f();
    }
catch (ExceptionB
 e) {
      ExceptionC
 c = new ExceptionC("exception
 a");
      throw c;
    }
  }
 
  public static void main(String[]
 args) {
      try {
        g();
      }
catch (ExceptionC
 e) {
        e.printStackTrace();
      }
  }
 
}
/*
exception.ExceptionC
at
 exception.NeverCaught.g(NeverCaught.java:12)
at
 exception.NeverCaught.main(NeverCaught.java:19)
*/

public class NeverCaught
 {
  static void f()
throws ExceptionB{
    throw new ExceptionB("exception
 b");
  }
 
  static void g()
throws ExceptionC
 {
    try {
      f();
    }
catch (ExceptionB
 e) {
      ExceptionC
 c = new ExceptionC("exception
 a");
      //异常连
      c.initCause(e);
      throw c;
    }
  }
 
  public static void main(String[]
 args) {
      try {
        g();
      }
catch (ExceptionC
 e) {
        e.printStackTrace();
      }
  }
 
}
/*
exception.ExceptionC
at
 exception.NeverCaught.g(NeverCaught.java:12)
at
 exception.NeverCaught.main(NeverCaught.java:21)
Caused
 by: exception.ExceptionB
at
 exception.NeverCaught.f(NeverCaught.java:5)
at
 exception.NeverCaught.g(NeverCaught.java:10)
...
 1 more
*/

public void readFile(String
 file) {
    BufferedReader
 reader = null;
    try {
      reader
 = new BufferedReader(new InputStreamReader(
          new FileInputStream(file)));
      //
 do some other work
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
    }
finally {
      try {
        reader.close();
      }
catch (IOException
 e) {
        e.printStackTrace();
      }
    }
  }

public void readFile()
 {
    BufferedReader
 reader = null;
    try {
      reader
 = new BufferedReader(new InputStreamReader(
          new FileInputStream("file")));
      //
 do some other work
     
      //close
 reader
      reader.close();
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
    }
catch (IOException
 e) {
      e.printStackTrace();
    }
  }
 

public void readFile()
 {
    BufferedReader
 reader = null;
    try {
      try {
        reader
 = new BufferedReader(new InputStreamReader(
            new FileInputStream("file")));
        //
 do some other work
 
        //
 close reader
      }
finally {
        reader.close();
      }
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
    }
catch (IOException
 e) {
      e.printStackTrace();
    }
  }

public class ResourceInConstructor
 {
  BufferedReader
 reader = null;
  public ResourceInConstructor()
 {
    try {
      reader
 = new BufferedReader(new InputStreamReader(new FileInputStream("")));
    }
catch (FileNotFoundException
 e) {
      e.printStackTrace();
    }
  }
   
  public void readFile()
 {
    try {
      while(reader.readLine()!=null)
 {
        //do
 some work
      }
    }
catch (IOException
 e) {
      e.printStackTrace();
    }
  }
   
  public void dispose()
 {
    try {
      reader.close();
    }
catch (IOException
 e) {
      e.printStackTrace();
    }
  }
}

 

public void readFile(String
 file) {
    BufferedReader
 reader = null;
    Connection
 conn = null;
    try {
      reader
 = new BufferedReader(new InputStreamReader(
          new FileInputStream(file)));
      //
 do some other work
       
      conn
 = DriverManager.getConnection("");
      //...
    }
catch (Exception
 e) {
      e.printStackTrace();
    }
finally {
      try {
        reader.close();
        conn.close();
      }
catch (Exception
 e) {
        e.printStackTrace();
      }
    }
  }