getrandomnumber.java

一些常用的java程序,包括swing.net.io,matrix等

package randonNumber;

public class GetRandomNumber {

	/**
	 * 	java.util.Random rd = new java.util.Random();
		rd.nextInt();  //get a unlimited integer, it can be positive or negative.
		rd.netxInt(max); //get a unnegative interger between 0(included) an max(unincluded)
		rd.nextDouble();//get a double between 0.0d(included) and 1.0d(unincluded)
		in java sdk, there is no GetRandomString()
		after new String(), there is a String, but it's empty, not null
		System.out.println(new String()); ==== SPACE 
	 * 
	 * 
	 */
	
	//-----------------------------------------------------------------
	
	public static int GetRandomInteger()
	{
		java.util.Random rd = new java.util.Random();
		return rd.nextInt();
	}
	
	//-----------------------------------------------------------------
	
	public static int GetRandomInteger(int bound)
	{
		java.util.Random rd = new java.util.Random();
		return rd.nextInt(bound);
	}
	
	//-----------------------------------------------------------------
	
	public static int GetRandomPositiveInteger(int bound)
	{
		java.util.Random rd = new java.util.Random();
		int rn;
		do
		{
			rn = rd.nextInt(bound);
		}while(rn == 0);
		return rn;
	}
	
	//-----------------------------------------------------------------
	
	public static double GetRanomDouble()
	{//the double is between 0.0d(include) and 1.0d(not include)
		java.util.Random rd = new java.util.Random();
		return rd.nextDouble();
	}
	
	//-----------------------------------------------------------------
	
	public static String GetRandomStringUnstrict()
	{ //get a String, may be null, may be " ";
		int maxlength = 16;
		String str = null;
		char [] source = {	'a','b','c','d','e','f','g','h','i','j','k','l','m','n',
							'o','p','q','r','s','t','u','v','w','x','y','z',    //0 - 25
							'A','B','C','D','E','F','G','H','I','J','K','L','M','N', //26 - 51
							'O','P','Q','R','S','T','U','V','W','X','Y','Z', //52 - 77
							'0','1','2','3','4','5','6','7','8','9',   //78 - 87
							'@','#','$','%',//88-91
							' '};  //92 SPACE, which means SPACE is the source.length_th char
		int len = GetRandomInteger(maxlength);  //len can be 0
		
		for(int i = 0; i < len; i++)
		{
			str += source[GetRandomInteger(source.length)];//source.length  - maxIndexofSource[] = 1,char can be SPACE
		}
		
		return str;
	}
	
	//-----------------------------------------------------------------
	
	public static String GetRandomString()
	{ //get a String, may be null, may be " ";
		int maxlength = 16;
		String str = new String();
		char [] source = {	'a','b','c','d','e','f','g','h','i','j','k','l','m','n',
							'o','p','q','r','s','t','u','v','w','x','y','z',    //0 - 25
							'A','B','C','D','E','F','G','H','I','J','K','L','M','N', //26 - 51
							'O','P','Q','R','S','T','U','V','W','X','Y','Z', //52 - 77
							'0','1','2','3','4','5','6','7','8','9',   //78 - 87
							'@','#','$','%',//88-91
							' '};  //92 SPACE, which means SPACE is the source.length_th char
		int len = GetRandomInteger(maxlength) + 1;  //len can't  be 0
		
		for(int i = 0; i < len; i++)
		{
			str += source[GetRandomInteger(source.length - 1)];//char[i] can'T be SAPCE
		}
		
		return str;
	}
	
	//-----------------------------------------------------------------
	
	public static String GetRandomString(int len)
	{ //get a String, can't be null or " ";
		String str = new String();
		char [] source = {	'a','b','c','d','e','f','g','h','i','j','k','l','m','n',
							'o','p','q','r','s','t','u','v','w','x','y','z',    //0 - 25
							'A','B','C','D','E','F','G','H','I','J','K','L','M','N', //26 - 51
							'O','P','Q','R','S','T','U','V','W','X','Y','Z', //52 - 77
							'0','1','2','3','4','5','6','7','8','9',   //78 - 87
							'@','#','$','%',//88-91
							' '};  //92 SPACE, which means SPACE is the source.length_th char
		
		for(int i = 0; i < len; i++)
		{
			str += source[GetRandomInteger(source.length - 1)];//char[i] can'T be SAPCE
		}
		
		return str;
	}
	
	//-----------------------------------------------------------------
	
	public static void Output(Object obj)
	{
		System.out.println(obj.getClass().getName()+ "  :  "+obj);		
	}
	
	//-----------------------------------------------------------------
	
	public static void main(String[] args)
	{
		java.util.Random rd = new java.util.Random();
		
		for(int i = 0; i < 100; i++)
		{
			System.out.println(rd.nextInt());
		}
		
		Output(GetRandomInteger());
		Output(GetRandomPositiveInteger(15));
		Output(GetRanomDouble());
		Output(GetRandomString());
		Output(GetRandomString(15));
	}
}