vector2d.java

MASON代表多主体邻里或网络仿真(Multi-Agent Simulator of Neighborhoods or Networks)。它是乔治梅森大学用Java开发的离散事件多主体仿真核心库

package sim.app.keepaway;
import java.io.Serializable;
import sim.util.Double2D;

public /*strictfp*/ class Vector2D implements Serializable
    {
    public double x;
    public double y;

    public Vector2D( double x, double y )
        {
        this.x = x;
        this.y = y;
        }

    public Vector2D( final Double2D d )
        {
        this.x = d.x;
        this.y = d.y;
        }

    public final Vector2D add( final Vector2D b )
        {
        return new Vector2D( x + b.x, y + b.y );
        }

    public final Vector2D add( final Double2D b )
        {
        return new Vector2D( x + b.x, y + b.y );
        }

    public final Vector2D subtract( final Vector2D b )
        {
        return new Vector2D( x - b.x, y - b.y );
        }

    public final Vector2D subtract( final Double2D b )
        {
        return new Vector2D( x - b.x, y - b.y );
        }

    public final Vector2D amplify( double alpha )
        {
        return new Vector2D( x * alpha, y * alpha );
        }

    public final Vector2D normalize()
        {
        if( x != 0 || y != 0 )
            {
            double temp = /*Strict*/Math.sqrt( x*x+y*y );
            return new Vector2D( x/temp, y/temp );
            }
        else
            return new Vector2D( 0, 0 );
        }

    public final double length()
        {
        return /*Strict*/Math.sqrt( x*x+y*y );
        }
    
    public final double angle()
        {
        double a = /*Strict*/Math.atan(y/x);
        if(x < 0)
            a += /*Strict*/Math.PI;
        return a;
        }

    public final Vector2D setLength( double dist )
        {
        if( dist == 0 )
            return new Vector2D( 0, 0 );
        if( x == 0 && y == 0 )
            return new Vector2D( 0, 0 );
        double temp = /*Strict*/Math.sqrt( x*x+y*y );
        return new Vector2D( x * dist / temp, y * dist / temp );
        }
    
    public final double getDistTo( Vector2D a )
        {
        double dx = x-a.x;
        double dy = y-a.y;
        return /*Strict*/Math.sqrt( dx*dx + dy*dy );
        }
    }