[ Java学习 ] 异常实验

题目：

//1.
import java.util.Arrays;
class MyException extends Exception
{
	MyException ( String s )
	{
		super(s);
	}
}


class Triangle
{
	double side[];
	
	Triangle()
	{
		
	}
	Triangle ( double a, double b, double c )
	{
		side = new double[3];
		side[0] = a; side[1] = b; side[2] = c;
		Arrays.sort(side);
	}
	
	double getArea() //Heron's formula
	{
		double p = 0.0, s;
		for (int i = 0; i < 3; i++) p += side[i];
		p /= 2;
		s = Math.sqrt(p * (p - side[0]) * (p - side[1]) * (p - side[2]) );
		return s;
	}
	void countArea()
	{
		boolean jud = true;
		try
		{
			for ( int i = 0; i < 3; i++ )
				if ( side[i] < 0)
					throw new MyException("Invalid input! You have input a negative !");
			
			if ( side[0] + side[1] <= side[2] )
				throw new MyException("Invalid input! The three sides can not form a triangle!");
		}
		catch (MyException e)
		{
			jud = false;
			System.out.println(e.toString());
		}
		
		if (jud)
		{
			System.out.println("The square for the triangle is " + getArea());
		}
		
	}
	
}
public class test1 
{
	
	public static void main(String[] args)
	{
		Triangle t[] = new Triangle[3];
		
		t[0] = new Triangle(-3, 4, 5);
		t[1] = new Triangle(1, 1, 3);
		t[2] = new Triangle(3, 4, 5);
		
		for (int i = 0; i < 3; i++)
		t[i].countArea();
	}

}

//2.(1)
import java.util.*;
class Student implements Comparable<Student>
{
	String name;
	double height;
	Student (String n, double h)
	{
		name = n;
		height = h;
	}
	Student ()
	{
		
	}
	
	public int compareTo(Student s)
	{
		if (this.height != s.height)
			return (this.height > s.height? 1 : -1); //身高不同按身高
		return this.name.compareTo(s.name); //身高相同按名字字典序
	}
	void display()
	{
		System.out.println(name + " " + height);
	}
}

class SetDemo
{
	TreeSet<Student> ts;
	
	void init()
	{
		Scanner sc = new Scanner(System.in);
		ts = new TreeSet<Student>();
		String []info = {"一", "二"};
		for (int i = 0; i < 2; i++)
		{
			System.out.println("请输入第" + info[i] + "个人的姓名");
			String n = "";
			double h = 0.0;
			n = sc.next();
			sc.nextLine(); // name
			
			boolean loop = true;
			while (loop)
			{
				System.out.println("请输入第" + info[i] + "个人的身高");
				try
				{
					h = sc.nextDouble();
					loop = false;
				}
				catch (InputMismatchException e)
				{
					System.out.println("身高数据有误，请重新输入！");
					sc.nextLine();
				}
			}
			Student s = new Student(n, h);
			ts.add(s);
		}
	}
	
	void solve()
	{
		System.out.println("----------------------------");
		System.out.println("按身高排序后的结果是：");
		Iterator<Student> it = ts.iterator();
		while (it.hasNext())
			it.next().display();
	}
}

public class test2 
{
	public static void main(String[] args)
	{
		SetDemo demo = new SetDemo();
		demo.init();
		demo.solve();
	}
}

//2.(2)用 Scanner 类的函数进行改写
//不用 try catch 来判断输入类型的合法性，而是改用 Scanner 类的函数来判断
import java.util.*;
class Student implements Comparable<Student>
{
	String name;
	double height;
	Student (String n, double h)
	{
		name = n;
		height = h;
	}
	Student ()
	{
		
	}
	
	public int compareTo(Student s)
	{
		if (this.height != s.height)
			return (this.height > s.height? 1 : -1); //身高不同按身高
		return this.name.compareTo(s.name); //身高相同按名字字典序
	}
	void display()
	{
		System.out.println(name + " " + height);
	}
}

class SetDemo
{
	TreeSet<Student> ts;
	
	void init()
	{
		Scanner sc = new Scanner(System.in);
		ts = new TreeSet<Student>();
		String []info = {"一", "二"};
		for (int i = 0; i < 2; i++)
		{
			System.out.println("请输入第" + info[i] + "个人的姓名");
			String n = "";
			double h = 0.0;
			n = sc.next();
			sc.nextLine(); // name
			
			boolean loop = true;
			while (loop)
			{
				System.out.println("请输入第" + info[i] + "个人的身高");
				if (sc.hasNextDouble())
				{
					h = sc.nextDouble();
					loop = false;
				}
				else
				{
					System.out.println("身高数据有误，请重新输入！");
					sc.nextLine();
				}
			}
			Student s = new Student(n, h);
			ts.add(s);
		}
	}
	
	void solve()
	{
		System.out.println("----------------------------");
		System.out.println("按身高排序后的结果是：");
		Iterator<Student> it = ts.iterator();
		while (it.hasNext())
			it.next().display();
	}
}


public class test2 
{
	public static void main(String[] args)
	{
		SetDemo demo = new SetDemo();
		demo.init();
		demo.solve();
	}
}

//3.

import java.util.*;
import java.util.TreeMap;

public class test3 
{
	public static void main(String []args)
	{
		TreeMap<String, Integer> map = new TreeMap<String, Integer>();
		String str = "aaa bbb ccc ccc ccc ccc bbb bbb aaa";
		Scanner sc = new Scanner(str);
		System.out.print("{");
		
		while (sc.hasNext())
		{
			String s = sc.next();
			if (!map.containsKey(s))
				map.put(s, new Integer(1));
			else
			{
				int val = map.get(s);
				map.put(s, new Integer(val + 1));
			}
		}
		
		Iterator<String> it = map.keySet().iterator();
		boolean first = true;
		while (it.hasNext())
		{
			if (first) first = false;
			else System.out.print(",");
			
			String s = it.next();
			System.out.print(s + "=" + map.get(s));
		}
		System.out.println("}");
	}
}

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