Java 冷门基础知识

public class Object
{
	
	public native int hashCode();

    public boolean equals(Object obj) {
        return (this == obj);
    }
	
}

public final class String implements java.io.Serializable, Comparable<String>, CharSequence
{
	
	public int hashCode() {
        int h = hash;
        if (h == 0 && value.length > 0) {
            char val[] = value;

            for (int i = 0; i < value.length; i++) {
                h = 31 * h + val[i];
            }
            hash = h;
        }
        return h;
    }
	
    public boolean equals(Object anObject) {
        if (this == anObject) {
            return true;
        }
        if (anObject instanceof String) {
            String anotherString = (String)anObject;
            int n = value.length;
            if (n == anotherString.value.length) {
                char v1[] = value;
                char v2[] = anotherString.value;
                int i = 0;
                while (n-- != 0) {
                    if (v1[i] != v2[i])
                        return false;
                    i++;
                }
                return true;
            }
        }
        return false;
    }

}

public final class Integer extends Number implements Comparable<Integer>
{
	
	@Override
    public int hashCode() {
        return Integer.hashCode(value);
    }

	public static int hashCode(int value) {
        return value;
    }
	
    public boolean equals(Object obj) {
        if (obj instanceof Integer) {
            return value == ((Integer)obj).intValue();
        }
        return false;
    }

}

public final class Long extends Number implements Comparable<Long>
{

    @Override
    public int hashCode() {
        return Long.hashCode(value);
    }

    public static int hashCode(long value) {
        return (int)(value ^ (value >>> 32));
    }
	
    public boolean equals(Object obj) {
        if (obj instanceof Long) {
            return value == ((Long)obj).longValue();
        }
        return false;
    }

}