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Java 16 New characteristics ：instanceof To strengthen
instanceof Keyword , It is mainly used to judge whether an object is an instance of a class .
example , Sometimes we have to deal with a data set similar to this ：
Map<String, Object> data = new HashMap<>();
data.put("key1", "aaa");
data.put("key2", 111);
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This Map Medium Value Because values can be different objects , So the definition is Object. This time , When we get When I came out , Judge and convert the needs before handling them .
example , Let's take out key1 Of value, Then the operation of intercepting a string , Just write it like this ：
Object value =data.get("key1");
if (value instanceof String) {
String s = (String) value;
System.out.println(s.substring(1));
}
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First identify the obtained value Can it be String, Then do forced type conversion , Then stop the operation on the string . This is the traditional way of writing , And in the Java 16 After the strengthening of , About instanceof Discrimination and type conversion can be combined into one , Therefore, the improved writing method can be as follows ：
Object value =data.get("key1");
if (value instanceof String s) {
System.out.println(s.substring(1));
}
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Isn't it much simpler ？ If you haven't used it , Try the operation quickly ！
Tips： This function has experienced 2 individual Preview edition （JDK 14 Medium JEP 305、JDK 15 Medium JEP 375）, Finalized on JDK 16 Medium JEP 394.
