Library Class

The access point for the JAR library is a class that extends the Library class. The library's main job is to list the tools that are available through the library; most often, the tools are all tools to add the various components defined - that is, instances of the AddTool class working with different component factories.


package com.cburch.gray;

import java.util.Arrays;
import java.util.List;


/** The library of components that the user can access. */
public class Components extends Library {
    /** The list of all tools contained in this library. Technically,
     * libraries contain tools, which is a slightly more general concept
     * than components; practically speaking, though, you'll most often want
     * to create AddTools for new components that can be added into the circuit.
    private List<AddTool> tools;
    /** Constructs an instance of this library. This constructor is how
     * Logisim accesses first when it opens the JAR file: It looks for
     * a no-arguments constructor method of the user-designated class.
    public Components() {
        tools = Arrays.asList(new AddTool[] {
                new AddTool(new GrayIncrementer()),
                new AddTool(new SimpleGrayCounter()),
                new AddTool(new GrayCounter()),
    /** Returns the name of the library that the user will see. */ 
    public String getDisplayName() {
        return "Gray Tools";
    /** Returns a list of all the tools available in this library. */
    public List<AddTool> getTools() {
        return tools;

Next: Simple Gray Code Counter.