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Java initialization method: class, container
Initialization class (non-final):
In the DefaultActionMapper class of Struts2:
public DefaultActionMapper() { prefixTrie = new PrefixTrie() { { put(METHOD_PREFIX, new ParameterAction() { public void execute(String key, ActionMapping mapping) { if (allowDynamicMethodCalls) { mapping.setMethod(key.substring( METHOD_PREFIX.length())); } } }); //。。。。 }}; }
put is the method of PrefixTrie: public void put(String prefix, Object value) ;
Initialize container:
Original method in collection framework (collections, such as list, map, set, etc.):
Set<String> myset = new HashSet<String>(); myset.add("aa"); myset.add("bb"); myset.add("cc"); myset.add("dd"); domethod(myset);
Static initialization Method:
private static final Set<String> myset = new HashSet<String>(); static { myset.add("aa"); myset.add("bb"); myset.add("cc"); myset.add("dd"); }
Double-brace syntax (double-brace syntax) creates and initializes a new collection:
private static final Set<String> myset = new HashSet<String>() {{ add("aa"); add("bb"); add("cc"); add("dd"); }};
doMethod(new HashSet<String>() {{ add("aa"); add("bb"); add("cc"); add("dd"); }});
First level of brackets It actually defines an internal anonymous class (Anonymous Inner Class);
The second layer of brackets is actually an instance initialization block ( instance initializer block), this block is executed during the construction of the inner anonymous class.
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