java 检查是否是数组 检查是否是空数组 检查数组是否包含某个元素

/**
* Determine whether the given object is an array:
* either an Object array or a primitive array.
* @param obj the object to check
*/
public static boolean isArray(Object obj) {
return (obj != null && obj.getClass().isArray());
}

/**
* Determine whether the given array is empty:
* i.e. {@code null} or of zero length.
* @param array the array to check
*/
public static boolean isEmpty(Object[] array) {
return (array == null || array.length == 0);
}

/**
* Check whether the given array contains the given element.
* @param array the array to check (may be {@code null},
* in which case the return value will always be {@code false})
* @param element the element to check for
* @return whether the element has been found in the given array
*/
public static boolean containsElement(Object[] array, Object element) {
if (array == null) {
return false;
}
for (Object arrayEle : array) {
if (nullSafeEquals(arrayEle, element)) {
return true;
}
}
return false;
}

/**
* Determine if the given objects are equal, returning {@code true}
* if both are {@code null} or {@code false} if only one is
* {@code null}.
* <p>Compares arrays with {@code Arrays.equals}, performing an equality
* check based on the array elements rather than the array reference.
* @param o1 first Object to compare
* @param o2 second Object to compare
* @return whether the given objects are equal
* @see java.util.Arrays#equals
*/
public static boolean nullSafeEquals(Object o1, Object o2) {
if (o1 == o2) {
return true;
}
if (o1 == null || o2 == null) {
return false;
}
if (o1.equals(o2)) {
return true;
}
if (o1.getClass().isArray() && o2.getClass().isArray()) {
if (o1 instanceof Object[] && o2 instanceof Object[]) {
return Arrays.equals((Object[]) o1, (Object[]) o2);
}
if (o1 instanceof boolean[] && o2 instanceof boolean[]) {
return Arrays.equals((boolean[]) o1, (boolean[]) o2);
}
if (o1 instanceof byte[] && o2 instanceof byte[]) {
return Arrays.equals((byte[]) o1, (byte[]) o2);
}
if (o1 instanceof char[] && o2 instanceof char[]) {
return Arrays.equals((char[]) o1, (char[]) o2);
}
if (o1 instanceof double[] && o2 instanceof double[]) {
return Arrays.equals((double[]) o1, (double[]) o2);
}
if (o1 instanceof float[] && o2 instanceof float[]) {
return Arrays.equals((float[]) o1, (float[]) o2);
}
if (o1 instanceof int[] && o2 instanceof int[]) {
return Arrays.equals((int[]) o1, (int[]) o2);
}
if (o1 instanceof long[] && o2 instanceof long[]) {
return Arrays.equals((long[]) o1, (long[]) o2);
}
if (o1 instanceof short[] && o2 instanceof short[]) {
return Arrays.equals((short[]) o1, (short[]) o2);
}
}
return false;
}

/**
* Check whether the given array of enum constants contains a constant with the given name,
* ignoring case when determining a match.
* @param enumValues the enum values to check, typically the product of a call to MyEnum.values()
* @param constant the constant name to find (must not be null or empty string)
* @return whether the constant has been found in the given array
*/
public static boolean containsConstant(Enum<?>[] enumValues, String constant) {
return containsConstant(enumValues, constant, false);
}

/**
* Check whether the given array of enum constants contains a constant with the given name.
* @param enumValues the enum values to check, typically the product of a call to MyEnum.values()
* @param constant the constant name to find (must not be null or empty string)
* @param caseSensitive whether case is significant in determining a match
* @return whether the constant has been found in the given array
*/
public static boolean containsConstant(Enum<?>[] enumValues, String constant, boolean caseSensitive) {
for (Enum<?> candidate : enumValues) {
if (caseSensitive ?
candidate.toString().equals(constant) :
candidate.toString().equalsIgnoreCase(constant)) {
return true;
}
}
return false;
}

/**
* Case insensitive alternative to {@link Enum#valueOf(Class, String)}.
* @param <E> the concrete Enum type
* @param enumValues the array of all Enum constants in question, usually per Enum.values()
* @param constant the constant to get the enum value of
* @throws IllegalArgumentException if the given constant is not found in the given array
* of enum values. Use {@link #containsConstant(Enum[], String)} as a guard to avoid this exception.
*/
public static <E extends Enum<?>> E caseInsensitiveValueOf(E[] enumValues, String constant) {
for (E candidate : enumValues) {
if (candidate.toString().equalsIgnoreCase(constant)) {
return candidate;
}
}
throw new IllegalArgumentException(
String.format("constant [%s] does not exist in enum type %s",
constant, enumValues.getClass().getComponentType().getName()));
}