What do the return values of Comparable compareTo mean in Java

Question

What is the difference between returning 0  returning 1 and returning -1 in compareTo   in Java

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int x   thisObject compareTo anotherObject     The compareTo   method returns an int with the following characteristics    negative If thisObject  lt  anotherObject zero If thisObject    anotherObject positive If thisObject  gt  anotherObject

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Answer in short   search your situation    1 compareTo 0   return  1  1 compareTo 1   return  0  0 comapreTo 1   return  -1

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Official Definition  From the reference docs of Comparable compareTo T       Compares this object with the   specified object for order  Returns a   negative integer  zero  or a positive   integer as this object is less than    equal to  or greater than the   specified object       The implementor must ensure   sgn x compareTo y        -sgn y compareTo x   for all x and y   This implies that x compareTo y  must   throw an exception iff y compareTo x    throws an exception        The implementor must also ensure that   the relation is transitive     x compareTo y  0  amp  amp  y compareTo z  0    implies x compareTo z  0       Finally  the implementor must ensure   that x compareTo y   0 implies that   sgn x compareTo z        sgn y compareTo z    for all z       It is strongly recommended  but not   strictly required that    x compareTo y   0      x equals y      Generally speaking  any class that   implements the Comparable interface   and violates this condition should   clearly indicate this fact  The   recommended language is  Note  this   class has a natural ordering that is   inconsistent with equals        In the foregoing description  the   notation sgn expression  designates   the mathematical signum function    which is defined to return one of -1    0  or 1 according to whether the value   of expression is negative  zero or   positive    My Version  In short   this compareTo that    returns    a negative int if this  lt  that 0 if this    that a positive int if this   that   where the implementation of this method determines the actual semantics of  lt   gt  and     I don t mean    in the sense of java s object identity operator   Examples   abc  compareTo  def     will yield something smaller than 0 as abc is alphabetically before def   Integer valueOf 2  compareTo Integer valueOf 1     will yield something larger than 0 because 2 is larger than 1   Some additional points  Note  It is good practice for a class that implements Comparable to declare the semantics of it s compareTo   method in the javadocs   Note  you should read at least one of the following    the Object Ordering section of the Collection Trail in the Sun Java Tutorial Effective Java by Joshua Bloch  especially item 12  Consider implementing Comparable Java Generics and Collections by Maurice Naftalin  Philip Wadler  chapter 3 1  Comparable   Warning  you should never rely on the return values of compareTo being -1  0 and 1  You should always test for x  lt  0  x    0  x  gt  0  respectively

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It can be used for sorting  and 0 means  equal  while -1  and 1 means  less  and  more  greater     Any return value that is less than 0 means that left operand is lesser  and if value is bigger than 0 then left operand is bigger

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take example if we want to compare  a  and  b   i e   a     this    negative int if a  lt  b if a    b Positive int if a   b

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System out println A compareTo B  gt 0  quot Yes quot   quot No quot   if the value of A gt B it will return  quot Yes quot  or  quot No quot

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I use this mnemonic    a compareTo b   lt  0    a  lt  b  a compareTo b   gt  0    a  gt  b  a compareTo b     0    a    b   You keep the signs and always compare the result of compareTo   to 0

[java] What do the return values of Comparable.compareTo mean in Java?

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