InterfaceAddress.java

/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.net;

/**
 * This class represents a Network Interface address. In short it's an
 * IP address, a subnet mask and a broadcast address when the address is
 * an IPv4 one. An IP address and a network prefix length in the case
 * of IPv6 address.
 *
 * @see java.net.NetworkInterface
 * @since 1.6
 */
// 网络接口的IP，包括网络IP和广播IP
public class InterfaceAddress {
    
    private InetAddress address = null;     // 网络IP
    private Inet4Address broadcast = null;  // 广播IP
    private short maskLength = 0;           // 掩码长度
    
    
    /**
     * Package private constructor. Can't be built directly, instances are
     * obtained through the NetworkInterface class.
     */
    InterfaceAddress() {
    }
    
    
    /**
     * Returns an {@code InetAddress} for this address.
     *
     * @return the {@code InetAddress} for this address.
     */
    // 获取网络IP
    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.
     *
     * @return the {@code InetAddress} representing the broadcast
     * address or {@code null} if there is no broadcast address.
     */
    // 获取广播IP
    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.
     */
    // 获取掩码长度
    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()
     */
    @Override
    public boolean equals(Object obj) {
        if(!(obj instanceof InterfaceAddress)) {
            return false;
        }
        
        InterfaceAddress cmp = (InterfaceAddress) obj;
        
        if(!(address == null ? cmp.address == null : address.equals(cmp.address))) {
            return false;
        }
        
        if(!(broadcast == null ? cmp.broadcast == null : broadcast.equals(cmp.broadcast))) {
            return false;
        }
        
        return maskLength == cmp.maskLength;
    }
    
    /**
     * Returns a hashcode for this Interface address.
     *
     * @return a hash code value for this Interface address.
     */
    @Override
    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.
     */
    @Override
    public String toString() {
        return address + "/" + maskLength + " [" + broadcast + "]";
    }
    
}