randomnum.java

来自「java写的bp神经网络的java程序」· Java 代码 · 共 45 行

package structure;
import java.util.Random;
/**
 * 产生随机数的singleton模式
 * */
public class RandomNum {
	private double up,down; 
    static RandomNum instance;
    Random ran;
    private RandomNum(){
    	ran=new Random(System.currentTimeMillis());
    }
    static RandomNum getInstance(){
        if(instance==null) instance=new RandomNum();	
        return instance;
    }
    /**
     * 设置产生的随机数的上下限
     * */
    public void setLimit(double up,double down){
    	if (up<down){
    	    this.up=down;
    	    this.down=up;
    	}
    	else{
    		this.up=up;
        	this.down=down;
    	}
    }
    /**
     * 产生位于上下限之间的double值
     * */
    public double getDouble(){
    	double r;
    	boolean isPos;                 //正数
    	for(;;){                       //先产生一个0-1之间的数
		    r=ran.nextDouble()*10;
		    isPos=ran.nextBoolean();
    		if (!isPos) r=-r;
		    if (r<down||r>up)continue;
		    return r;
	    }
    }
}