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Java Base == & equals

  Tags:  Integer cache, == , equals This Blogger emphasizes that in actual development, developers should prioritize using .equals() to compare object values ​​rather than simply relying on == to compare references. Java's Integer cache mechanism provides memory optimization for Java programs with values ​​in the range of -128 to 127.However, values ​​outside this range will result in the creation of new objects, resulting in unexpected results in == comparisons.       public static void main(String[] args) {         Integer a = 228;         Integer b = 228;         System.out.println(a == b); // false         Integer x = 1;         Integer y = 1;         System.out.println(x == y); // true         Integer c = 228;         Integer d = 228;         System.out.println(System.identityHash...
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Double.NaN Float.NaN

Double.NaN  Float.NaN double i = 0.0/0.0; double i = Double.NaN; equals http://docs.oracle.com/javase/7/docs/api/java/lang/Double.html public boolean equals( Object  obj) Compares this object against the specified object. The result is true if and only if the argument is not null and is a Double object that represents a double that has the same value as the double represented by this object. For this purpose, two double values are considered to be the same if and only if the method doubleToLongBits(double) returns the identical long value when applied to each. Note that in most cases, for two instances of class Double , d1 and d2 , the value of d1.equals(d2) is true if and only if d1.doubleValue() == d2.doubleValue() also has the value true . However, there are two exceptions: If d1 and d2 both represent Double.NaN , then the equals method returns true , even though Double.NaN==Double.NaN has the value ...
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Comparison of C Sharp and Java

If you only take care about technical details, please read directly: https://en.wikipedia.org/wiki/Comparison_of_C_Sharp_and_Java. The following contents based my learning curve and work background show the difference between them.  I am a software engineer, not research and development(R & D) personnel ( the former is like a construction worker ). The technical support documents and tools are important for software projects and application development. The developer and after-sales service all need the technical support documents; Good tools are sure be better for working performance efficiency and construction quality. For the technical support documents, intuitive feelings are Microsoft's better than Oracl's.  Microsoft's documents is easy to read and to get started. The implementation in documents is described in the table below. Microsoft Oracle (Sun) Who (is the reader) Grade 6 must be a bachelor's degree or more ...
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