clarifying this Java code and few ambiguities of this bot code

Question

I am working on this Chess bot code, in Java which is new to me. While I understand most of the what the code does, I am not sure I do understand it a full extent. In addition to that there is few things that confuses me in the code. for example this private d a; I thought we need to specify the type of every variable in Java. also this

private static final b h = new b((State)null, 1.0D / 0.0);

are we declaring b or h? and what doies 1.0D / 0.0 ? doesn't sound like a normal variable.

here is the full code:

public abstract class AIBot extends Bot {
    private d a;
    private int b;
    private int c;
    private boolean d;
    private boolean e;
    private c f;
    private static final Comparator g = new a();
    private static final b h = new b((State)null, 1.0D / 0.0);
    private static final b i = new b((State)null, -1.0D / 0.0);

    public AIBot(String var1, d var2, int var3, boolean var4, boolean var5, InputStream var6) {
        super(var1);
        this.c = 0;
        this.a = var2;
        this.b = var3 << 1;
        this.d = var4;
        this.e = var5;
        if (var6 == null) {
            this.f = null;
        } else {
            try {
                this.f = new c(var6);
            } catch (IOException var7) {
                throw new RuntimeException("Failed to read opening book", var7);
            }
        }
    }

    public AIBot(String var1, d var2, int var3, boolean var4, boolean var5) {
        this(var1, var2, var3, false, false, (InputStream)null);
    }

    protected State chooseMove(State var1) {
        State var2 = null;
        if (this.f != null) {
            var2 = this.f.a(var1);
        }

        if (var2 == null) {
            State var3 = var1;
            Player var8 = var1.player;
            AIBot var7 = this;
            b var4 = null;

            for(int var6 = 2; var6 <= var7.b; var6 += 2) {
                var7.c = var6;
                b var5 = var7.a(var8, var3, 0, -1.0D / 0.0, 1.0D / 0.0);
                if (var4 == null) {
                    var4 = var5;
                }

                if (var3.searchLimitReached()) {
                    break;
                }

                var4 = var5;
            }

            State var9;
            for(var9 = var4.a; var9.previous != var3; var9 = var9.previous) {
            }

            var2 = var9;
        }

        return var2;
    }

    private final Iterable a(Iterable var1) {
        if (!this.d) {
            return var1;
        } else {
            PriorityQueue var2 = new PriorityQueue(g);
            Iterator var3 = var1.iterator();

            while(var3.hasNext()) {
                State var4 = (State)var3.next();
                var2.add(var4);
                if (var4.searchLimitReached()) {
                    break;
                }
            }

            return var2;
        }
    }

    private final b a(Player var1, State var2, int var3, double var4, double var6) {
        if (this.a(var2, var3)) {
            return new b(var2, this.a.a(var2, var1));
        } else {
            b var8 = i;
            Iterator var10 = this.a(var2.next()).iterator();

            while(var10.hasNext()) {
                State var9 = (State)var10.next();
                b var10000 = var8;
                int var10004 = var3 + 1;
                double var17 = var6;
                double var15 = var4;
                int var12 = var10004;
                State var11 = var9;
                Player var21 = var1;
                AIBot var20 = this;
                b var10001;
                if (this.a(var11, var12)) {
                    var10001 = new b(var11, this.a.a(var11, var1));
                } else {
                    b var13 = h;
                    Iterator var19 = this.a(var11.next()).iterator();

                    while(var19.hasNext()) {
                        State var14 = (State)var19.next();
                        b var23 = var20.a(var21, var14, var12 + 1, var15, var17);
                        if ((var13 = var23.b < var13.b ? var23 : var13).b <= var15) {
                            break;
                        }

                        var17 = Math.min(var17, var13.b);
                        if (var11.searchLimitReached()) {
                            break;
                        }
                    }

                    var10001 = var13;
                }

                b var22 = var10001;
                var8 = var10000;
                if ((var8 = var22.b > var8.b ? var22 : var8).b >= var6) {
                    break;
                }

                var4 = Math.max(var4, var8.b);
                if (var2.searchLimitReached()) {
                    break;
                }
            }

            return var8;
        }
    }

    private final boolean a(State var1, int var2) {
        if (var1.over) {
            return true;
        } else if (var1.searchLimitReached()) {
            return true;
        } else if (var2 < this.c) {
            return false;
        } else if (this.e) {
            return var1.board.countPieces() == var1.previous.board.countPieces() || var2 >= this.c * 3;
        } else {
            return true;
        }
    }
}

Answer 1

private d a; - the fact that d or anything is in lowercase doesn't mean it has to variable. d is valid class name. You must remember that first you have object type - d and then variable name - a.

1.0D / 0.0 is also ok. D at the end of literal means that its type is double. Therefore something like this is ok: double d = 1.0D;, but float d = 1.0D; will rise an error. Dividing Double by ZERO will result is something called positive infinity, see constant: Double.POSITIVE_INFINITY.