import java.util.Iterator; ParticleSystem ps; Particle p; void setup(){ size(200,200); smooth(); ps = new ParticleSystem(new PVector(width/2,50)); } void draw(){ background(100); PVector gravity = new PVector(0,0.1); ps.applyForce(gravity); ps.addParticle(); ps.run(); } class Par…

Why NullPointerException

jiajia April 23, 2022, 7:55am 3

OH,Your help made me instantly enlightened.very thanks.

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