java 兩個 基礎點

/*
* 
*
*java 自帶工具類  分析 
*
*
*/
package java.util;
public final class Objects {
    private Objects() {
        throw new AssertionError("No java.util.Objects instances for you!");
    }
    public static boolean equals(Object a, Object b) {
        return (a == b) || (a != null && a.equals(b));
    }
// 深度 對象相等比較
    public static boolean deepEquals(Object a, Object b) {
        if (a == b)
            return true;
        else if (a == null || b == null)
            return false;
        else
            return Arrays.deepEquals0(a, b);
    }
// hash碼獲取
    public static int hashCode(Object o) {
        return o != null ? o.hashCode() : 0;
    }
// 數組的hashcode
    public static int hash(Object... values) {
        return Arrays.hashCode(values);
    }
    public static String toString(Object o) {
        return String.valueOf(o);
    }
// 帶默認值的 toString 方法
    public static String toString(Object o, String nullDefault) {
        return (o != null) ? o.toString() : nullDefault;
    }
// 自定義 比較
    public static <T> int compare(T a, T b, Comparator<? super T> c) {
        return (a == b) ? 0 :  c.compare(a, b);
    }
// 不爲空判斷
    public static <T> T requireNonNull(T obj) {
        if (obj == null)
            throw new NullPointerException();
        return obj;
    }
// 不空判斷 帶字符提示
    public static <T> T requireNonNull(T obj, String message) {
        if (obj == null)
            throw new NullPointerException(message);
        return obj;
    }
// 是否爲空
    public static boolean isNull(Object obj) {
        return obj == null;
    }
    public static boolean nonNull(Object obj) {
        return obj != null;
    }
    public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
        if (obj == null)
            throw new NullPointerException(messageSupplier.get());
        return obj;
    }
}