src/java.base/share/classes/java/net/InterfaceAddress.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * under the terms of the GNU General Public License version 2 only, as
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 * particular file as subject to the "Classpath" exception as provided
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package java.net;

import java.util.Objects;

/**
 * This class represents a Network Interface address. In the case of
 * IPv4, this comprises the IP address, a subnet mask, and a broadcast
 * address if the interface supports broadcast. In the case of IPv6,
 * it comprises the IP address and a network prefix length.
 *
 * @see java.net.NetworkInterface
 * @since 1.6
 */
public final class InterfaceAddress {
    private InetAddress address = null;
    private Inet4Address broadcast = null;
    private short        maskLength = 0;

    /*
     * This constructor is called via JNI in NetworkInterface.c
     */
    private InterfaceAddress() {
    }

    /**
     * Returns an {@code InetAddress} for this address.
     *
     * @return the {@code InetAddress} for this address.
     */
    public InetAddress getAddress() {
        return address;
    }

    /**
     * Returns an {@code InetAddress} for the broadcast address
     * for this InterfaceAddress.
     * <p>
     * Only IPv4 networks have broadcast address therefore, in the case
     * of an IPv6 network, {@code null} will be returned.
     * <p>
     * Certain network interfaces, such as the loopback interface, do not support
     * broadcasting and will also return {@code null}.
     *
     * @return the {@code InetAddress} representing the broadcast
     *         address or {@code null} if there is no broadcast address.
     */
    public InetAddress getBroadcast() {
        return broadcast;
    }

    /**
     * Returns the network prefix length for this address. This is also known
     * as the subnet mask in the context of IPv4 addresses.
     * Typical IPv4 values would be 8 (255.0.0.0), 16 (255.255.0.0)
     * or 24 (255.255.255.0). <p>
     * Typical IPv6 values would be 128 (::1/128) or 10 (fe80::203:baff:fe27:1243/10)
     *
     * @return a {@code short} representing the prefix length for the
     *         subnet of that address.
     */
     public short getNetworkPrefixLength() {
        return maskLength;
    }

    /**
     * Compares this object against the specified object.
     * The result is {@code true} if and only if the argument is
     * not {@code null} and it represents the same interface address as
     * this object.
     * <p>
     * Two instances of {@code InterfaceAddress} represent the same
     * address if the InetAddress, the prefix length and the broadcast are
     * the same for both.
     *
     * @param   obj   the object to compare against.
     * @return  {@code true} if the objects are the same;
     *          {@code false} otherwise.
     * @see     java.net.InterfaceAddress#hashCode()
     */
    public boolean equals(Object obj) {
        return obj instanceof InterfaceAddress cmp &&
                Objects.equals(address, cmp.address) &&
                Objects.equals(broadcast, cmp.broadcast) &&
                maskLength == cmp.maskLength;
    }

    /**
     * Returns a hashcode for this Interface address.
     *
     * @return  a hash code value for this Interface address.
     */
    public int hashCode() {
        return address.hashCode() + ((broadcast != null) ? broadcast.hashCode() : 0) + maskLength;
    }

    /**
     * Converts this Interface address to a {@code String}. The
     * string returned is of the form: InetAddress / prefix length [ broadcast address ].
     *
     * @return  a string representation of this Interface address.
     */
    public String toString() {
        return address + "/" + maskLength + " [" + broadcast + "]";
    }

}