Hardworking Strawberry

1.GravitationalForce
　0:GravitationalConstant:-1.0 (正值表引力，負值表斥力)
　1:Distance:-1.0
　2:BarnesHutTheta:0.9

2. DragForce (穩定)
　0:DragCoefficient:0.01

3. SpringForce
　0:SpringCoefficient:1.0E-4
　1:DefaultSpringLength:50.0 (edge長短)

1. Set Label Size
　Iterator iter = vis.items("graph.nodes");
　while ( iter.hasNext() ) {
　　　VisualItem item = (VisualItem)iter.next();
　　　item.setSize(4)
　}

2. Read Data
　Iterator iter = vis.items("graph.nodes");
　while ( iter.hasNext() ) {
　　　VisualItem item = (VisualItem)iter.next();
　　　double tw = item.getDouble("weight");
　}