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();
			}
		}
	}

//声明变量  
var attr1 = 1;  
var attr2 = 1.03;  
var attr3 = "hello";  
var attr4 = false; 

//声明变量  
var attr0 ;  
var attr1 = 1;  
var attr2 = 1.03;  
var attr3 = "hello";  
var attr4 = false;  
              
alert(typeof attr0); //undefined  
alert(typeof attr1); //number  
alert(typeof attr2); //number    
alert(typeof attr3); //string  
alert(typeof attr4); //boolean  
alert(typeof null); //object  
alert(typeof undefined); //undefined  

// 作用域  
var outer = 1;  
function layer() {  
    var layer1 = 2;  
    function inner() {  
        var layer2 = 3;  
        alert(layer1);//2  
        alert(layer2);//3  
    }  
    inner();  
}  
layer();  
              
alert(outer);//1  
alert(layer1);//layer1已经被回收  
alert(layer2);//layer2已经被回收 

// sample2   
var x = "smile";  
var alerts = function() {  
    alert(x); //undefined  
    var x = "fuck";   
    alert(x); //fuck  
          
    //上面的相当于下面的代码  
    //var x ;  
    //alert(x); //undefined  
    //x = "fuck";  
    //alert(x); //fuck  
}  

 //闭包演示  
var func = function() {  
    var attr = "can read me??";  
    return function() {  
        alert(attr);  
    }  
}  
func()(); 

var car = new Object();  
car.color = "red";  
car.speed = 100;  
car.showColor = function() {  
    alert(this.color);  
};  
  
car.showColor();  

function createCar() {  
    var car = new Object();  
    car.color = "red";  
    car.speed = 100;  
    car.showColor = function() {  
        alert(this.color);  
    };  
    return car;  
}  
var car = createCar();  
car.showColor();  

function Car(color, speed) {  
    this.color = color;  
    this.speed = speed;  
    this.showColor = function() {  
        alert(this.color);  
    };  
}  
var car = new Car("blue", 400);  
car.showColor();  

function Car() {  
}  
Car.prototype.color = "blue";  
Car.prototype.speed = 300;  
Car.prototype.showColor = function() {  
    alert(this.color);  
};  
var car = new Car();  
car.showColor();  

function Car(color, speed) {  
    this.color = color;  
    this.speed = speed;  
    this.drivers = new Array("mike", "sue");  
}  
Car.prototype.showColor = function() {  
    alert(this.color);  
};  
var car1 = new Car("green", 300);  
car1.drivers.push("wangkang");  
car1.showColor();  
alert(car1.drivers.join());  
  
var car2 = new Car("black", 300);  
car2.showColor();  
alert(car2.drivers.join());  

function Car(color, speed) {  
    this.color = color;  
    this.speed = speed;  
    this.drivers = new Array("mike", "sue");  
}  
if (typeof Car._initialized == "undefined") {  
    Car.prototype.showColor = function() {  
        alert(this.color);  
    };  
    Car._initialized = true;  
}  
var car1 = new Car("green", 300);  
car1.drivers.push("wangkang");  
car1.showColor();  
alert(car1.drivers.join());  
  
var car2 = new Car("black", 300);  
car2.showColor();  
alert(car2.drivers.join());  

function Car() {  
    var car = new Object();  
    car.color = "red";  
    car.speed = 100;  
    car.showColor = function() {  
        alert(this.color);  
    };  
    return car;  
}  
var car = new Car();  
car.showColor();