本章主要分析　公開屬性與私有屬性提供公開get、set方法兩種方式對比

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// Degenerate classes like this should not be public! class Point { public double x; public double y; }

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// Public class with exposed immutable fields - questionable public final class Time { private static final int HOURS_PER_DAY = 24; private static final int MINUTES_PER_HOUR = 60; public final int hour; public final int minute; public Time(int hour, int minute) { if (hour < 0 || hour >= HOURS_PER_DAY) throw new IllegalArgumentException("Hour: " + hour); if (minute < 0 || minute >= MINUTES_PER_HOUR) throw new IllegalArgumentException("Min: " + minute); this.hour = hour; this.minute = minute; } ... // Remainder omitted }

Certainly, the hard-liners are correct when it comes to public classes:

if a class?is accessible outside its package, provide accessor methods, to preserve the

flexibility to change the class’s internal representation. If a public class exposes its
data fields, all hope of changing its representation is lost, as client code can be distributed
far and wide.

如果我們直接公開域，我們將無法對屬性進行限制，這樣會導致，在調用該處的代碼都要添加上限制，而修改次數隨著調用的次數而增加，

如果我們提供get，set方法，就能容易的在set方法內對傳入參數進行限制。

轉載于:https://www.cnblogs.com/linkarl/p/5663952.html

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