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This noncompliant code example defines a Comparator with a compare() method [Bloch 2009]. The compare() method accepts two boxed primitives as arguments. The == operator is used to compare the two boxed primitives. In this context, however, it compares the references to the wrapper objects rather than comparing the values held in those objects.

import java.util.Comparator;
 
static Comparator<Integer> cmp = new Comparator<Integer>() {
  public int compare(Integer i, Integer j) {
    return i < j ? -1 : (i == j ? 0 : 1);
  } 
};

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This compliant solution uses the comparison operators, <, >, <=, or >=, because these cause automatic unboxing of the primitive values. The == and != operators should not be used to compare boxed primitives.

import java.util.Comparator;
 
static Comparator<Integer> cmp = new Comparator<Integer>() { 
  public int compare(Integer i, Integer j) {
    return i < j ? -1 : (i > j ? 1 : 0) ;
  }
};

Noncompliant Code Example

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