java 的 linq，不要再写令人讨厌的 for 了！

Posted 2020-08-26 大胡子毛绒老头

package com.ly.linq;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;

public class Enm {
    public static <T> ArrayList<T> notNull(Iterable<T> source) {
        return where(source, new Pre<T>() {
            @Override
            public boolean check(T t) {
                return t != null;
            }
        });
    }

    public static <T> ArrayList<T> where(T[] ts, Pre<T> mapper) {
        return where(toList(ts), mapper);
    }

    public static <T> ArrayList<T> where(Iterable<T> source, Pre<T> mapper) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t : source) {
            if (mapper.check(t)) {
                r.add(t);
            }
        }
        return r;
    }

    public static <T> String toString(T[] source, Object s) {
        return toString(toList(source), s);
    }

    public static <T> String toString(T[] source, Object s, FuncT<T, String> mapper) {
        return toString(toList(source), s, mapper);
    }

    public static <T> String toString(Iterable<T> source, Object s) {
        return toString(source, s, null);
    }

    public static <T> String toString(Iterable<T> source, Object spliter, FuncT<T, String> mapper) {
        String s = spliter == null ? "" : spliter.toString();
        StringBuilder sb = new StringBuilder();
        for (T ti : source) {
            String str = mapper == null ? ti.toString() : mapper.get(ti);
            sb.append(str + s);
        }
        if (sb.length() > 0) {
            sb.setLength(sb.length() - s.length());
            return sb.toString();
        } else {
            return "";
        }
    }

    public static <T, TKey, TValue> HashMap<TKey, TValue> toHashMap(T[] ts, FuncT<T, Pair<TKey, TValue>> pair) {
        return toHashMap(toList(ts), pair);
    }

    public static <T, TKey, TValue> HashMap<TKey, TValue> toHashMap(Iterable<T> source, FuncT<T, Pair<TKey, TValue>> pair) {
        HashMap<TKey, TValue> r = new HashMap<TKey, TValue>();
        for (T t : source) {
            Pair<TKey, TValue> p = pair.get(t);
            r.put(p.getKey(), p.getValue());
        }
        return r;
    }

    public static <T> ArrayList<T> toList(Iterable<T> source) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t : source) {
            r.add(t);
        }
        return r;
    }

    public static <T> ArrayList<T> toList(T[] ts) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t : ts) {
            r.add(t);
        }
        return r;
    }

    public static <T> ArrayList<T> except(Iterable<T> it0, Iterable<T> it1) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t : it0) {
            if (!r.contains(t)) {
                r.add(t);
            }
        }
        for (int i = r.size() - 1; i > -1; i--) {
            T t = r.get(i);
            if (contains(it1, t)) {
                r.remove(t);
            }
        }
        return r;
    }

    public static <T> ArrayList<T> union(Iterable<T> it0, Iterable<T> it1) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t : it0) {
            if (!r.contains(t)) {
                r.add(t);
            }
        }
        for (T t : it1) {
            if (!r.contains(t)) {
                r.add(t);
            }
        }
        return r;
    }

    public static <T> ArrayList<T> intersect(Iterable<T> it0, Iterable<T> it1) {
        ArrayList<T> r = new ArrayList<T>();
        for (T t0 : it0) {
            for (T t1 : it1) {
                if (t0 == null) {
                    if (t1 == null) {
                        if (!r.contains(t0)) {
                            r.add(t0);
                        }
                    }
                } else {
                    if (t0.equals(t1)) {
                        if (!r.contains(t0)) {
                            r.add(t0);
                        }
                    }
                }
            }
        }
        return r;
    }

    public static <T0, T1, TOut> ArrayList<TOut> intersect(Class<TOut> outCls, Iterable<T0> it0, Iterable<T1> it1, FuncT<T0, TOut> mapper0, FuncT<T1, TOut> mapper1) {
        ArrayList<TOut> r = new ArrayList<TOut>();
        for (T0 t0 : it0) {
            TOut t0out = mapper0.get(t0);
            for (T1 t1 : it1) {
                TOut t1out = mapper1.get(t1);
                if (t0out == null) {
                    if (t1out == null) {
                        if (!r.contains(t0out)) {
                            r.add(null);
                        }
                    }
                } else {
                    if (t0out.equals(t1out)) {
                        if (!r.contains(t0out)) {
                            r.add(t0out);
                        }
                    }
                }
            }
        }
        return r;
    }

    public static <T> boolean existsIn(T t, T... ts) {
        for (T t2 : ts) {
            if (t.equals(t2)) {
                return true;
            }
        }
        return false;
    }

    public static <T> boolean contains(Iterable<T> source, T target) {
        for (T t : source) {
            if (t == null) {
                if (target == null) {
                    return true;
                }
            } else {
                if (t.equals(target)) {
                    return true;
                }
            }
        }
        return false;
    }

    public static <T> boolean any(Pre<T> pre, T t, T... ts) {
        if (pre.check(t)) {
            return true;
        }
        return any(toList(ts), pre);
    }

    public static <T> boolean any(T[] ts, Pre<T> pre) {
        return any(toList(ts), pre);
    }

    public static <T> boolean any(Iterable<T> source, Pre<T> pre) {
        for (T i : source) {
            if (pre.check(i)) {
                return true;
            }
        }
        return false;
    }

    public static <T> ArrayList<T> sort(ArrayList<T> source, FuncT<T, Integer> mapper) {
        int[] indexes = sortIndexes(source, mapper);
        ArrayList<T> r = new ArrayList<T>();
        for (int i : indexes) {
            r.add(source.get(i));
        }
        return r;
    }

    public static <T> int[] sortIndexes(Iterable<T> source, FuncT<T, Integer> mapper) {
        ArrayList<Integer> ints = new ArrayList<Integer>();
        Iterator<T> it = source.iterator();
        while (it.hasNext()) {
            Integer integer = mapper.get(it.next());
            ints.add(integer);
        }
        int[] r = new int[ints.size()];
        for (int i = 0; i < r.length; i++) {
            r[i] = ints.get(i);
        }
        return sortIndexes(r);
    }

    public static <T> int[] sortIndexes(T[] source, FuncT<T, Integer> mapper) {
        int[] ints = new int[source.length];
        for (int i = 0; i < source.length; i++) {
            ints[i] = mapper.get(source[i]);
        }
        return sortIndexes(ints);
    }

    public static int[] sortIndexes(int[] source) {
        ArrayList<Integer> decre = new ArrayList<Integer>();
        for (int i : source) {
            decre.add(i);
        }
        ArrayList<Integer> incre = new ArrayList<Integer>();
        while (incre.size() < source.length) {
            int s = 0;
            int v = decre.get(0);
            for (int i = 1; i < decre.size(); i++) {
                int e = decre.get(i);
                if (e < v) {
                    s = i;
                    v = e;
                }
            }
            decre.remove(s);
            for (int i = 0; i < source.length; i++) {
                if (source[i] != v || incre.contains(i)) {
                    continue;
                }
                incre.add(i);
                break;
            }
        }
        int[] r = new int[incre.size()];
        for (int i = 0; i < incre.size(); i++) {
            r[i] = incre.get(i);
        }
        return r;
    }

    public static <TIn, TOut> ArrayList<TOut> select(TIn[] source, FuncT<TIn, TOut> mapper) {
        return select(toList(source), mapper);
    }

    public static <TIn, TOut> ArrayList<TOut> select(Iterable<TIn> source, FuncT<TIn, TOut> mapper) {
        ArrayList<TOut> r = new ArrayList<TOut>();
        for (TIn ti : source) {
            r.add(mapper.get(ti));
        }
        return r;
    }
}