Swing本来提供的滑块JSlider丑的实在不忍直视,所以很有必要进行优化重写
提供有两种方法进行JSlider的美化

运用look and feel

那什么是 LookAndFeel 呢？
通俗的说，这就是皮肤；
从功能上说。这是一种批量管理 Swing 控件外观的机制；
从根源来说，这是 Swing 的核心。

在Swing中只需一行代码就可以改变皮肤
UIManager.setLookAndFeel(new LookAndFeel());
比如:
UIManager.setLookAndFeel(new QuaquaLookAndFeel());
我们还可以通过
UIManager.setLookAndFeel(String s);
来改变外观,其中,s是表示该外观的路径,比如
UIManager.setLookAndFeel("org.fife.plaf.OfficeXP.OfficeXPLookAndFeel");

以下是一些java自带的look and feel,当然还可以去网上下载其他的.

UIManager.setLookAndFeel(com.sun.java.swing.plaf.windows.WindowsLookAndFeel.class.getName());//还可以，只能在windows系统中用，也就是这句代码不跨平台
UIManager.setLookAndFeel(javax.swing.plaf.nimbus.NimbusLookAndFeel.class.getName());//还可以
UIManager.setLookAndFeel(javax.swing.plaf.basic.BasicLookAndFeel.class.getName());//swing默认的丑皮肤
UIManager.setLookAndFeel(javax.swing.plaf.metal.MetalLookAndFeel.class.getName());//swing默认的丑皮肤
UIManager.setLookAndFeel(com.sun.java.swing.plaf.motif.MotifLookAndFeel.class.getName());//丑
UIManager.setLookAndFeel(com.sun.java.swing.plaf.gtk.GTKLookAndFeel.class.getName());//还可以

重写JSlider UI

JSlider playTime = new JSlider();

playTime.setUI(new  javax.swing.plaf.metal.MetalSliderUI(){
	    	@Override
	    	public void paintThumb(Graphics g) {
                //绘制指示物
	    		Graphics2D g2d = (Graphics2D) g;
	    		g2d.setColor(Color.white);
	    		g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
	    		g2d.fillOval(thumbRect.x, thumbRect.y, thumbRect.width,
                        thumbRect.height);//修改为圆形
                //也可以帖图(利用鼠标事件转换image即可体现不同状态)
                //g2d.drawImage(image, thumbRect.x, thumbRect.y, thumbRect.width,thumbRect.height,null);

	    	}
	    	public void paintTrack(Graphics g) {
                //绘制刻度的轨迹
	    		int cy,cw;
	    		Rectangle trackBounds = trackRect;
	    		if (slider.getOrientation() == JSlider.HORIZONTAL) {
	    			Graphics2D g2 = (Graphics2D) g;
	    			g2.setPaint(Color.black);//将背景设为黑色
	    			cy = (trackBounds.height/2) - 2;
	    			cw = trackBounds.width;
	    			
	    			g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
	    					RenderingHints.VALUE_ANTIALIAS_ON);
	    			g2.translate(trackBounds.x, trackBounds.y + cy);
	    			g2.fillRect(0, -cy + 5, cw, cy);
	    			
	    			int trackLeft = 0;
	    			int trackRight = 0;
	    			trackRight = trackRect.width - 1;

	    			int middleOfThumb = 0;
	    			int fillLeft = 0;
	    			int fillRight = 0;
	    			//换算坐标
	    			middleOfThumb = thumbRect.x + (thumbRect.width / 2);
	    			middleOfThumb -= trackRect.x;
	    			
	    			if (!drawInverted()) {
	    				fillLeft = !slider.isEnabled() ? trackLeft : trackLeft + 1;
	    				fillRight = middleOfThumb;
	    				} else {
	    				fillLeft = middleOfThumb;
	    				fillRight = !slider.isEnabled() ? trackRight - 1
	    				: trackRight - 2;
	    				}
	    			//设定渐变,在这里从红色变为红色,则没有渐变,滑块划过的地方自动变成红色
	    			g2.setPaint(new GradientPaint(0, 0, Color.red, cw, 0,
	    					Color.red, true));
	    			g2.fillRect(0, -cy + 5, fillRight - fillLeft, cy);
	    					
	    			g2.setPaint(slider.getBackground());
	    			g2.fillRect(10, 10, cw, 5);

	    			g2.setPaint(Color.WHITE);
	    			g2.drawLine(0, cy, cw - 1, cy);

	    			g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
	    			RenderingHints.VALUE_ANTIALIAS_OFF);
	    			g2.translate(-trackBounds.x, -(trackBounds.y + cy));   					
	    		}
	    		else {
    				super.paintTrack(g);
    				}
	    	}
	    
});

效果图