Java homework

Java homework

NO.1: Generics(泛型)

package cn.com.hrbust.Test;

public class Generics {
 public static void main(String[]args) {
  Chorus<Singer, Instrument>model = new Chorus<Singer,Instrument>();
  Singer JJ = new Singer();
  Instrument piano = new Instrument();
  model.makeChorus(JJ, piano);
 }
}
class Chorus<E,F> {
 void makeChorus(E person,F instrument) {
  person.toString();
  instrument.toString();
 }
}
class Singer {
 public String toString() {
  System.out.println("lalallala");
  return "";
 }
}
class Instrument {
 public String toString() {
  System.out.println("|455|8784|");
  return "";
 }
}

No.2：Exception（异常）

package cn.com.hrbust.Test;

public class Exception {
 public static void main(String[]args) {
  B b = new B();
  try {
   b.f(100);
   b.f(-9);
  } catch (MyException e) {
   System.out.println(e.getMessage());
  }
 }
}

class MyException extends Throwable {
 String message;
 MyException(int n) {
  message = n+"不是正数";
 }
 public String getMessage() {
  return message;
 }
}
class B{
 public void f(int n) throws MyException {
  if(n<0) {
   MyException e = new MyException(n);
   throw(e);
  }
  double number = Math.sqrt(n);
  System.out.println(n+"的平方根："+number);
 }
}

No.3：内部类VS外部类

package nice;

public class InnerClassDemo {
 public static void main(String[]args) {
//  Outer o = new Outer();
//  Outer.Inner inner = o.new Inner();
//   inner.display();
  Outer outer = new Outer();
  outer.inst();
 }
}
class Outer {
 int score = 100;
 void inst() {
  class Inner {
   void display() {
    System.out.println("score is "+score);
   }
  }
  Inner inner = new Inner();
  inner.display();
 }
// class Inner {
//  String name = "zhangsan";
//  void display() {
//   System.out.println("score is "+score);
//  }
 }
// public void print() {
//  Inner inner = new Inner();
//  System.out.println(inner.name);
// }

 NO.4：与接口有关的内部类

package cn.com.hrbust.Test;

interface Show {
 public void show();
}
class A {
 void f(Show s) {
  s.show();
 }
}
public class Interface {
 public static void main(String[]args) {
  A a = new A();
  a.f(new Show() {
   public void show() {
    System.out.println("Hello");
   }
  });
 }
}

NO.5：Integer。parseInt and Integer.toString

package cn.com.hrbust.Test;

public class Test {
 public static void main(String[]args)throws NumberFormatException
 {
  System.out.println(Integer.parseInt("285527")+1);
  System.out.println(Integer.toString(123)+1);
 }
}