光子CI之旅

既然Effective Java和Guava都誕生于Google，那么當(dāng)他們相遇會(huì)什么樣呢，為此我決定重溫Effective Java這部著作，并針對(duì)每一條規(guī)則尋找Guava給出的解決方案，希望能更深入的掌握J(rèn)ava。

Effective Java第10條規(guī)則： 始終要覆蓋toString方法

Effective Java里指出，"建議所有的子類都覆蓋這個(gè)toString方法"，這樣可以使類用起來更加舒適。最重要的是這樣的做法對(duì)調(diào)試非常有幫助，Guava通過 Objects.toStringHelper為我們提供了方便創(chuàng)建toString的方法。看下面的樣例：

// Returns "ClassName{x=1}"
   Objects.toStringHelper(this)
       .add("x", 1)
       .toString();

   // Returns "MyObject{x=1}"
   Objects.toStringHelper("MyObject")
       .add("x", 1)
       .toString();

Guava關(guān)于toString的文檔連接： https://code.google.com/p/guava-libraries/wiki/CommonObjectUtilitiesExplained

下面我把Effective Java的樣例代碼列出，并用Guava重新了toString方法

// 重寫PhoneNumber的toString方法 - Effective Java中文第二版第44頁
package org.effectivejava.examples.chapter03.item10;

import java.util.HashMap;
import java.util.Map;

import com.google.common.base.Objects;

public final class PhoneNumber {
        private final short areaCode;
        private final short prefix;
        private final short lineNumber;

        public PhoneNumber(int areaCode, int prefix, int lineNumber) {
                rangeCheck(areaCode, 999, "area code");
                rangeCheck(prefix, 999, "prefix");
                rangeCheck(lineNumber, 9999, "line number");
                this.areaCode = (short) areaCode;
                this.prefix = (short) prefix;
                this.lineNumber = (short) lineNumber;
        }

        private static void rangeCheck(int arg, int max, String name) {
                if (arg < 0 || arg > max)
                        throw new IllegalArgumentException(name + ": " + arg);
        }

        @Override
        public boolean equals(Object o) {
                if (o == this)
                        return true;
                if (!(o instanceof PhoneNumber))
                        return false;
                PhoneNumber pn = (PhoneNumber) o;
                return pn.lineNumber == lineNumber && pn.prefix == prefix
                                && pn.areaCode == areaCode;
        }

        @Override
        public int hashCode() {
                int result = 17;
                result = 31 * result + areaCode;
                result = 31 * result + prefix;
                result = 31 * result + lineNumber;
                return result;
        }

    //Effective Java原有的toString方法
        /*
         * @Override public String toString() { return
         * String.format("(%03d) %03d-%04d", areaCode, prefix, lineNumber); }
         */

        /**
         * 采用Guava實(shí)現(xiàn)的toString
         *
         */
        @Override
        public String toString() {
                return Objects.toStringHelper(this)
                                .addValue(String.format("(%03d) %03d-%04d", areaCode, prefix,lineNumber))
                                .add("areaCode", areaCode)
                                .add("prefix", prefix)
                                .add("lineNumber", lineNumber)
                                .toString();
        }

        public static void main(String[] args) {
                Map<PhoneNumber, String> m = new HashMap<PhoneNumber, String>();
                m.put(new PhoneNumber(707, 867, 5309), "Jenny");

                System.out.println(m);
        }
}

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