java 源碼frist 之 Boolean 、Byte

Boolean

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

    /**
     * Returns a hash code for a {@code boolean} value; compatible with
     * {@code Boolean.hashCode()}.
     *
     * @param value the value to hash
     * @return a hash code value for a {@code boolean} value.
     * @since 1.8
     */
    public static int hashCode(boolean value) {
        return value ? 1231 : 1237;
    }

布爾類型的hashCode ture  爲 1231  false 1237；

boolean 類型 進行比較  true 與false 比較大小

  public static int compare(boolean x, boolean y) {
        return (x == y) ? 0 : (x ? 1 : -1);
    }

boolean 的靜態方法 

    /**
     * Returns the result of applying the logical AND operator to the
     * specified {@code boolean} operands.
     *
     * @param a the first operand
     * @param b the second operand
     * @return the logical AND of {@code a} and {@code b}
     * @see java.util.function.BinaryOperator
     * @since 1.8
     */
    public static boolean logicalAnd(boolean a, boolean b) {
        return a && b;
    }

    /**
     * Returns the result of applying the logical OR operator to the
     * specified {@code boolean} operands.
     *
     * @param a the first operand
     * @param b the second operand
     * @return the logical OR of {@code a} and {@code b}
     * @see java.util.function.BinaryOperator
     * @since 1.8
     */
    public static boolean logicalOr(boolean a, boolean b) {
        return a || b;
    }

    /**
     * Returns the result of applying the logical XOR operator to the
     * specified {@code boolean} operands.
     *
     * @param a the first operand
     * @param b the second operand
     * @return  the logical XOR of {@code a} and {@code b}
     * @see java.util.function.BinaryOperator
     * @since 1.8
     */
    public static boolean logicalXor(boolean a, boolean b) {
        return a ^ b;
    }

1.8以上新加的功能  用來  求兩個 boolean 的 | & ^

 

byte

byte 的緩存數據類

 private static class ByteCache {
        private ByteCache(){}

        static final Byte cache[] = new Byte[-(-128) + 127 + 1];

        static {
            for(int i = 0; i < cache.length; i++)
                cache[i] = new Byte((byte)(i - 128));
        }
    }

 

Byte 獲取某個值的Byte  本質從Byte 緩存中取出

    public static Byte valueOf(byte b) {
        final int offset = 128;
        return ByteCache.cache[(int)b + offset];
    }