惰性空间分配 lazy space allocation

最新推荐文章于 2024-07-31 11:48:18 发布

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本文介绍了一种称为懒加载的设计模式，这种模式强调资源的延迟分配，即直到确实需要时才进行资源分配。通过一个Java示例，展示了如何实现懒加载模式来管理不同类型水果的实例，仅在首次请求特定类型时创建其实例。

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Lazy allocation simply means not allocating a resource until it is actually needed.

Here is an example in Java:

public class Fruit {
 
    private static final Map<String,Fruit> types = new HashMap<String, Fruit>();
    private final String type;
 
    // using a private constructor to force use of the factory method.
    private Fruit(String type) {
        this.type = type;
    }
 
    /**
    * Lazy Factory method, gets the Fruit instance associated with a
    * certain type. Instantiates new ones as needed.
    * @param type Any string that describes a fruit type, e.g. "apple"
    * @return The Fruit instance associated with that type.
    */
    public static synchronized Fruit getFruit(String type) {
        if(!types.containsKey(type)) {
            types.put(type, new Fruit(type)); // Lazy initialization
        }
        return types.get(type);
    }
 
}