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只由静态字段和静态方法
组成的类,像工具类,这些类不能被实例化
,只通过类直接调用静态方法和使用静态字段,就将该类的构造方法设为私有的,jdk中java.util.Arrays
、java.util.Collections
和java.lang.Math
都遵循这个原则
public class Arrays {
// Suppresses default constructor, ensuring non-instantiability.
private Arrays() {}
}
public class Collections {
// Suppresses default constructor, ensuring non-instantiability.
private Collections() {}
}
public final class Math {
/**
* Don't let anyone instantiate this class.
*/
private Math() {}
}