Spring util工具類ObjectUtils源碼

package org.springframework.util;

import java.lang.reflect.Array;
import java.util.Arrays;

/**
*該工具類采用抽象類定義，抽象類內部全采用靜態方法
*通常情況下定義工具類有如下方法：
*Method I:定義final類，私有化構造函數，類內部全采用靜態方法
*Method II:定義abstract類，類內部全采用靜態方法
*Method III:不建議采用接口+靜態方法 或者 非私有化構造函數+靜態方法
 */
public abstract class ObjectUtils {
    /** 初始Hash*/
    private static final int INITIAL_HASH = 7;
    /** Hash乘數*/
    private static final int MULTIPLIER = 31;

    /** 邏輯空串*/
    private static final String EMPTY_STRING = "";
    /** 實際空串*/
    private static final String NULL_STRING = "null";
    /** 數組開始*/
    private static final String ARRAY_START = "{";
    /** 數組結尾*/
    private static final String ARRAY_END = "}";
    private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END;
    /** 數組分隔符*/
    private static final String ARRAY_ELEMENT_SEPARATOR = ", ";


    //判斷對象是否為可檢查異常，即是RuntimeException或Error的實例
    public static boolean isCheckedException(Throwable ex) {
        return !(ex instanceof RuntimeException || ex instanceof Error);
    }

    //是否可兼容異常，即是繼承自RuntimeException和Error的異常或者自定義的declaredExceptions的實例
    public static boolean isCompatibleWithThrowsClause(Throwable ex, Class<?>... declaredExceptions) {
        if (!isCheckedException(ex)) {
            return true;
        }
        if (declaredExceptions != null) {
            for (Class<?> declaredException : declaredExceptions) {
                if (declaredException.isInstance(ex)) {
                    return true;
                }
            }
        }
        return false;
    }

    //判斷對象是否為數組obj.getClass().isArray()
    public static boolean isArray(Object obj) {
        return (obj != null && obj.getClass().isArray());
    }

    //判斷數組為空
    public static boolean isEmpty(Object[] array) {
        return (array == null || array.length == 0);
    }

    //判斷數組包含元素
    public static boolean containsElement(Object[] array, Object element) {
        if (array == null) {
            return false;
        }
        for (Object arrayEle : array) {
            //非空安全相等，即在同為空值時默認不相等
            if (nullSafeEquals(arrayEle, element)) {
                return true;
            }
        }
        return false;
    }

    //包含常量，對枚舉類型有效
    public static boolean containsConstant(Enum<?>[] enumValues, String constant) {
        return containsConstant(enumValues, constant, false);
    }

    //包含常量，對枚舉類型有效，大小寫敏感
    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;
    }

    //枚舉類型的大小寫不敏感valueOf()
    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()));
    }

    //數組添加元素，被添加的元素必須是A元素的子類以保證數組元素類型的一致性
    public static <A, O extends A> A[] addObjectToArray(A[] array, O obj) {
        //首先默認為最頂級的Object類型，如果array不空采用A，否則如果obj不空采用O，否則就是默認的Object類型
        Class<?> compType = Object.class;
        if (array != null) {
            compType = array.getClass().getComponentType();
        }
        else if (obj != null) {
            compType = obj.getClass();
        }
        int newArrLength = (array != null ? array.length + 1 : 1);
        @SuppressWarnings("unchecked")
        //調用Array工具類的newInstance來創建數組對象
        A[] newArr = (A[]) Array.newInstance(compType, newArrLength);
        if (array != null) {
            System.arraycopy(array, 0, newArr, 0, array.length);
        }
        newArr[newArr.length - 1] = obj;
        return newArr;
    }

    //轉為Object數組，不管是什么類型的數組統統轉為Object數組的表達方式
    public static Object[] toObjectArray(Object source) {
        if (source instanceof Object[]) {
            return (Object[]) source;
        }
        if (source == null) {
            return new Object[0];
        }
        if (!source.getClass().isArray()) {
            throw new IllegalArgumentException("Source is not an array: " + source);
        }
        int length = Array.getLength(source);
        if (length == 0) {
            return new Object[0];
        }
        Class<?> wrapperType = Array.get(source, 0).getClass();
        Object[] newArray = (Object[]) Array.newInstance(wrapperType, length);
        for (int i = 0; i < length; i++) {
            newArray[i] = Array.get(source, i);
        }
        return newArray;
    }


    //直接調用Arrays.equals()來判斷基本數據類型數組，其他的調用equals()來比較，具體的取決於equals()的實現
    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;
    }

    //求得hashCode，當值為null時，hashCode為0
    public static int nullSafeHashCode(Object obj) {
        if (obj == null) {
            return 0;
        }
        if (obj.getClass().isArray()) {
            if (obj instanceof Object[]) {
                return nullSafeHashCode((Object[]) obj);
            }
            if (obj instanceof boolean[]) {
                return nullSafeHashCode((boolean[]) obj);
            }
            if (obj instanceof byte[]) {
                return nullSafeHashCode((byte[]) obj);
            }
            if (obj instanceof char[]) {
                return nullSafeHashCode((char[]) obj);
            }
            if (obj instanceof double[]) {
                return nullSafeHashCode((double[]) obj);
            }
            if (obj instanceof float[]) {
                return nullSafeHashCode((float[]) obj);
            }
            if (obj instanceof int[]) {
                return nullSafeHashCode((int[]) obj);
            }
            if (obj instanceof long[]) {
                return nullSafeHashCode((long[]) obj);
            }
            if (obj instanceof short[]) {
                return nullSafeHashCode((short[]) obj);
            }
        }
        return obj.hashCode();
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(Object[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (Object element : array) {
            hash = MULTIPLIER * hash + nullSafeHashCode(element);
        }
        return hash;
    }
    
    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(boolean[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (boolean element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(byte[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (byte element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(char[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (char element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(double[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (double element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(float[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (float element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(int[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (int element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(long[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (long element : array) {
            hash = MULTIPLIER * hash + hashCode(element);
        }
        return hash;
    }
    
    // 31*7+e1.hashCode() 31*(31*7+e1.hashCode())+e2.hashCode()......
    public static int nullSafeHashCode(short[] array) {
        if (array == null) {
            return 0;
        }
        int hash = INITIAL_HASH;
        for (short element : array) {
            hash = MULTIPLIER * hash + element;
        }
        return hash;
    }

    //boolean值就兩個hash值，1231和1237
    public static int hashCode(boolean bool) {
        return (bool ? 1231 : 1237);
    }

    
    /**
    直接調用Double.hashCode(value);
     long bits = doubleToLongBits(value);
      return (int)(bits ^ (bits >>> 32));
    */
    public static int hashCode(double dbl) {
        return hashCode(Double.doubleToLongBits(dbl));
    }

    //同上
    public static int hashCode(float flt) {
        return Float.floatToIntBits(flt);
    }

    //同上
    public static int hashCode(long lng) {
        return (int) (lng ^ (lng >>> 32));
    }

    //object轉字符串，基本上等同於obj.toString(),唯一不同的是空對象仍然有效
    //與String.valueOf(obj)也類似，但是空對象是“”而不是"null"
    public static String identityToString(Object obj) {
        if (obj == null) {
            return EMPTY_STRING;
        }
        return obj.getClass().getName() + "@" + getIdentityHexString(obj);
    }

    
    public static String getIdentityHexString(Object obj) {
        return Integer.toHexString(System.identityHashCode(obj));
    }

    //轉成顯示的字符串，將數組顯示出來
    public static String getDisplayString(Object obj) {
        if (obj == null) {
            return EMPTY_STRING;
        }
        return nullSafeToString(obj);
    }

    
    public static String nullSafeClassName(Object obj) {
        return (obj != null ? obj.getClass().getName() : NULL_STRING);
    }

    //對數組進行了處理，其余的類似String.valueOf(obj)
    public static String nullSafeToString(Object obj) {
        if (obj == null) {
            return NULL_STRING;
        }
        if (obj instanceof String) {
            return (String) obj;
        }
        if (obj instanceof Object[]) {
            return nullSafeToString((Object[]) obj);
        }
        if (obj instanceof boolean[]) {
            return nullSafeToString((boolean[]) obj);
        }
        if (obj instanceof byte[]) {
            return nullSafeToString((byte[]) obj);
        }
        if (obj instanceof char[]) {
            return nullSafeToString((char[]) obj);
        }
        if (obj instanceof double[]) {
            return nullSafeToString((double[]) obj);
        }
        if (obj instanceof float[]) {
            return nullSafeToString((float[]) obj);
        }
        if (obj instanceof int[]) {
            return nullSafeToString((int[]) obj);
        }
        if (obj instanceof long[]) {
            return nullSafeToString((long[]) obj);
        }
        if (obj instanceof short[]) {
            return nullSafeToString((short[]) obj);
        }
        String str = obj.toString();
        return (str != null ? str : EMPTY_STRING);
    }

    
    public static String nullSafeToString(Object[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(String.valueOf(array[i]));
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(boolean[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(byte[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(char[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append("'").append(array[i]).append("'");
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(double[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(float[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }

            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(int[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(long[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

    
    public static String nullSafeToString(short[] array) {
        if (array == null) {
            return NULL_STRING;
        }
        int length = array.length;
        if (length == 0) {
            return EMPTY_ARRAY;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            if (i == 0) {
                sb.append(ARRAY_START);
            }
            else {
                sb.append(ARRAY_ELEMENT_SEPARATOR);
            }
            sb.append(array[i]);
        }
        sb.append(ARRAY_END);
        return sb.toString();
    }

}