java 限定控制台输入值的类型

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class 控制输入类型 {
static InputStreamReader in;
static BufferedReader reader;
static
{in=new InputStreamReader(System.in);
reader=new BufferedReader(in);
}

//控制输入为String
static String readString()
{String s="";
try
{ s=reader.readLine();

}
catch(IOException e)
{System.out.println(e);
System.exit(0);
}
return s;
}

//控制输入为char
static char readChar()
{char ch=‘a‘;
try
{
String s=readString();
ch=s.charAt(0);

}
catch(Exception e)
{System.out.println("输入的数据类型不对，程序将退出");
System.exit(0);
}
return ch;
}

//控制输入为int
static int readInt()
{String s=readString();
int i=0;
try{
i=Integer.parseInt(s);
}
catch(Exception e)
{System.out.println("输入的数据类型不对，程序将退出");
System.exit(0);
}
return i;
}

//控制输入为double
static double readDouble()
{String s=readString();
double d=0.0;
try
{d=Double.parseDouble(s);
}
catch(Exception e)
{System.out.println("输入的数据类型不对，程序将退出");
System.exit(0);
}
return d;
}

//控制输入为float
static float readFloat()
{
String s=readString();
float f=0.0f;
try
{
f=Float.parseFloat(s);
}
catch(Exception e)
{ System.out.println("输入的数据类型不对，程序将退出");
System.exit(0);
}
return f;
}

}