如何解决问题:不能取消引用int [英] How to solve the problem: int cannot be dereferenced

问题描述

在这里，我有一些值，其中两个是整数，并且由于它们未被引用，因此无法在它们上调用方法.我该如何解决?

Here I have some value which two of them are integer and I can't call a method on them since they are not reference. How can I solve this?

String srcAddr, dstAddr, protocol;
int srcPort, dstPort;

public int hashCode() {

        final int prime = 31;
        int result = 1;
        result = prime * result + ((dstAddr == null) ? 0 : dstAddr.hashCode());
        result = prime * result + ((dstPort == null) ? 0 : dstPort.hashCode());
        result = prime * result + ((srcAddr == null) ? 0 : srcAddr.hashCode());
        result = prime * result + ((srcPort == null) ? 0 : srcPort.hashCode());
        return result;

}

此外，我也有一个相等的方法，下面显示了一部分错误，该错误与上面的相同，我无法将int与null进行比较.

Also, I have an equal method too, a part of it with the error is shown below ,which the same as above I can not compare int with a null.

@Override
public boolean equals(Object obj) {

    if (srcPort == null) {
        if (other.srcPort != null)
            return false;
    } else if (!srcPort.equals(other.srcPort))
        return false;

    if (srcPort == null) {
        if (other.srcPort != null)
            return false;
    } else if (!srcPort.equals(other.srcPort))
        return false;
}

如何解决此错误?

推荐答案

对于 hashcode 方法，您可以直接保留整数.整数是它们自己的hascodes.对于 equals 方法，只需使用 = 进行比较即可.因此代码变为:

For the hashcode method, you can just leave the ints as they are. Ints are their own hascodes. For the equals method, just compare them using =. So the code becomes:

public class Connection {

    String srcAddr, dstAddr, protocol; int srcPort, dstPort;

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((dstAddr == null) ? 0 : dstAddr.hashCode());
        result = prime * result + dstPort;
        result = prime * result
                + ((protocol == null) ? 0 : protocol.hashCode());
        result = prime * result + ((srcAddr == null) ? 0 : srcAddr.hashCode());
        result = prime * result + srcPort;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Connection other = (Connection) obj;
        if (dstAddr == null) {
            if (other.dstAddr != null)
                return false;
        } else if (!dstAddr.equals(other.dstAddr))
            return false;
        if (dstPort != other.dstPort)
            return false;
        if (protocol == null) {
            if (other.protocol != null)
                return false;
        } else if (!protocol.equals(other.protocol))
            return false;
        if (srcAddr == null) {
            if (other.srcAddr != null)
                return false;
        } else if (!srcAddr.equals(other.srcAddr))
            return false;
        if (srcPort != other.srcPort)
            return false;
        return true;
    }

}

编写 hashCode 和 equals 的正确实现非常棘手.更好地使用您的IDE生成它们.这也是我在这里所做的.

Writing correct implementations of hashCode and equals is tricky. Better use your IDE to generate them. That's what I did here too.

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