常用集合equals方法

HashMap（继承）

AbstractMap

    public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Map))
            return false;
        Map<?,?> m = (Map<?,?>) o;
        if (m.size() != size())
            return false;

        try {
            Iterator<Entry<K,V>> i = entrySet().iterator();
            while (i.hasNext()) {
                Entry<K,V> e = i.next();
                K key = e.getKey();
                V value = e.getValue();
                if (value == null) {
                    if (!(m.get(key)==null && m.containsKey(key)))
                        return false;
                } else {
                    if (!value.equals(m.get(key)))
                        return false;
                }
            }
        } catch (ClassCastException unused) {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }

        return true;
    }

HashSet（继承）

AbstractSet

    public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Set))
            return false;
        Collection<?> c = (Collection<?>) o;
        if (c.size() != size())
            return false;
        try {
            return containsAll(c);
        } catch (ClassCastException unused)   {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }
    }

Hashtable（重写）

    public synchronized boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Map))
            return false;
        Map<?,?> t = (Map<?,?>) o;
        if (t.size() != size())
            return false;

        try {
            Iterator<Map.Entry<K,V>> i = entrySet().iterator();
            while (i.hasNext()) {
                Map.Entry<K,V> e = i.next();
                K key = e.getKey();
                V value = e.getValue();
                if (value == null) {
                    if (!(t.get(key)==null && t.containsKey(key)))
                        return false;
                } else {
                    if (!value.equals(t.get(key)))
                        return false;
                }
            }
        } catch (ClassCastException unused)   {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }

        return true;
    }

TreeMap（重写）

public boolean equals(Object o) {
    if (!(o instanceof Map.Entry))
         return false;
     Map.Entry<?,?> e = (Map.Entry<?,?>)o;

     return valEquals(key,e.getKey()) && valEquals(value,e.getValue());
 }

TreeSet（继承）

AbstractSet

    public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Set))
            return false;
        Collection<?> c = (Collection<?>) o;
        if (c.size() != size())
            return false;
        try {
            return containsAll(c);
        } catch (ClassCastException unused)   {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }
    }

LinkedHashMap

AbstractMap

    public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Map))
            return false;
        Map<?,?> m = (Map<?,?>) o;
        if (m.size() != size())
            return false;

        try {
            Iterator<Entry<K,V>> i = entrySet().iterator();
            while (i.hasNext()) {
                Entry<K,V> e = i.next();
                K key = e.getKey();
                V value = e.getValue();
                if (value == null) {
                    if (!(m.get(key)==null && m.containsKey(key)))
                        return false;
                } else {
                    if (!value.equals(m.get(key)))
                        return false;
                }
            }
        } catch (ClassCastException unused) {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }

        return true;
    }

LinkedHashSet

AbstractSet

public boolean equals(Object o) {
    if (o == this)
        return true;

    if (!(o instanceof Set))
        return false;
    Collection<?> c = (Collection<?>) o;
    if (c.size() != size())
        return false;
    try {
        return containsAll(c);
    } catch (ClassCastException unused)   {
        return false;
    } catch (NullPointerException unused) {
        return false;
    }
}

IdentityHashMap

public boolean equals(Object o) {
     if (o == this) {
         return true;
     } else if (o instanceof IdentityHashMap) {
         IdentityHashMap<?,?> m = (IdentityHashMap<?,?>) o;
         if (m.size() != size)
             return false;

         Object[] tab = m.table;
         for (int i = 0; i < tab.length; i+=2) {
             Object k = tab[i];
             if (k != null && !containsMapping(k, tab[i + 1]))
                 return false;
         }
         return true;
     } else if (o instanceof Map) {
         Map<?,?> m = (Map<?,?>)o;
         return entrySet().equals(m.entrySet());
     } else {
         return false;  // o is not a Map
     }
 }

WeakHashMap

AbstractMap

    public boolean equals(Object o) {
        if (o == this)
            return true;

        if (!(o instanceof Map))
            return false;
        Map<?,?> m = (Map<?,?>) o;
        if (m.size() != size())
            return false;

        try {
            Iterator<Entry<K,V>> i = entrySet().iterator();
            while (i.hasNext()) {
                Entry<K,V> e = i.next();
                K key = e.getKey();
                V value = e.getValue();
                if (value == null) {
                    if (!(m.get(key)==null && m.containsKey(key)))
                        return false;
                } else {
                    if (!value.equals(m.get(key)))
                        return false;
                }
            }
        } catch (ClassCastException unused) {
            return false;
        } catch (NullPointerException unused) {
            return false;
        }

        return true;
    }

Arrays

public static boolean equals(long[] a, long[] a2) {
    if (a==a2)
        return true;
    if (a==null || a2==null)
        return false;

    int length = a.length;
    if (a2.length != length)
        return false;

    for (int i=0; i<length; i++)
        if (a[i] != a2[i])
            return false;

    return true;
}

LinkedList

AbstractList

public boolean equals(Object o) {
    if (o == this)
        return true;
    if (!(o instanceof List))
        return false;

    ListIterator<E> e1 = listIterator();
    ListIterator<?> e2 = ((List<?>) o).listIterator();
    while (e1.hasNext() && e2.hasNext()) {
        E o1 = e1.next();
        Object o2 = e2.next();
        if (!(o1==null ? o2==null : o1.equals(o2)))
            return false;
    }
    return !(e1.hasNext() || e2.hasNext());
}

Vector

AbstractList

public synchronized boolean equals(Object o) {
    return super.equals(o);
}

父亲

public boolean equals(Object o) {
   if (o == this)
       return true;
   if (!(o instanceof List))
       return false;

   ListIterator<E> e1 = listIterator();
   ListIterator<?> e2 = ((List<?>) o).listIterator();
   while (e1.hasNext() && e2.hasNext()) {
       E o1 = e1.next();
       Object o2 = e2.next();
       if (!(o1==null ? o2==null : o1.equals(o2)))
           return false;
   }
   return !(e1.hasNext() || e2.hasNext());
}

Stack

AbstractList

    public boolean equals(Object o) {
        if (o == this)
            return true;
        if (!(o instanceof List))
            return false;

        ListIterator<E> e1 = listIterator();
        ListIterator<?> e2 = ((List<?>) o).listIterator();
        while (e1.hasNext() && e2.hasNext()) {
            E o1 = e1.next();
            Object o2 = e2.next();
            if (!(o1==null ? o2==null : o1.equals(o2)))
                return false;
        }
        return !(e1.hasNext() || e2.hasNext());
    }