Java Set.hashCode方法代码示例

import java.util.Set; //导入方法依赖的package包/类
public static void main(String[] args) throws Exception {
    final ConcurrentHashMap<String, String> concurrentHashMap =
        new ConcurrentHashMap<>();

    concurrentHashMap.put("One", "Un");
    concurrentHashMap.put("Two", "Deux");
    concurrentHashMap.put("Three", "Trois");

    Set<Map.Entry<String, String>> entrySet = concurrentHashMap.entrySet();
    HashSet<Map.Entry<String, String>> hashSet = new HashSet<>(entrySet);

    if (false == hashSet.equals(entrySet)) {
        throw new RuntimeException("Test FAILED: Sets are not equal.");
    }
    if (hashSet.hashCode() != entrySet.hashCode()) {
        throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
    }
}
 

import java.util.Set; //导入方法依赖的package包/类
@Override
public int hashCode() {
  // Warning: this is broken if size() == 0, so it is critical that we
  // substitute an empty ImmutableSet to the user in place of this

  // It's a weird formula, but tests prove it works.
  int adjust = size() - 1;
  for (int i = 0; i < axes.size(); i++) {
    adjust *= 31;
    adjust = ~~adjust;
    // in GWT, we have to deal with integer overflow carefully
  }
  int hash = 1;
  for (Set<E> axis : axes) {
    hash = 31 * hash + (size() / axis.size() * axis.hashCode());

    hash = ~~hash;
  }
  hash += adjust;
  return ~~hash;
}
 

import java.util.Set; //导入方法依赖的package包/类
/**
 * Because Enums don't have stable hash codes, we can't use their hash code directly.  Instead
 * we want to use the has code of the enum's name, which should be stable.  Here we essentially
 * duplicate the hash code calculation of Map, using the stable hash code instead
 * @return stable hash code
 */
private static int _calculateStableHashCode(final Map<TrinidadAgent.Application, Set<AgentMatcher>> selectorAgents,
                                            final Set<AgentMatcher> capTouchMatchers)
{
  int hashCode = 0;

  // Map hash code is defined as the additive hash code of the entries
  for (Map.Entry<TrinidadAgent.Application, Set<AgentMatcher>> entry : selectorAgents.entrySet())
  {
    // use the enum's name to have a stable hash code
    int stableKeyHashCode = entry.getKey().name().hashCode();

    // entry hash code is defined as the XOR of the key and value.
    int entryHashCode = stableKeyHashCode ^ entry.getValue().hashCode();

    hashCode += entryHashCode;
  }

  hashCode += capTouchMatchers.hashCode();

  return hashCode;
}
 

import java.util.Set; //导入方法依赖的package包/类
public static void main(String[] args) throws Exception {
    final IdentityHashMap<String, String> identityHashMap =
        new IdentityHashMap<>();

    identityHashMap.put("One", "Un");
    identityHashMap.put("Two", "Deux");
    identityHashMap.put("Three", "Trois");

    Set<Map.Entry<String, String>> entrySet = identityHashMap.entrySet();
    HashSet<Map.Entry<String, String>> hashSet = new HashSet<>(entrySet);

    // NB: These comparisons are valid in this case because none of the
    //     keys put into 'identityHashMap' above are equal to any other.
    if (false == hashSet.equals(entrySet)) {
        throw new RuntimeException("Test FAILED: Sets are not equal.");
    }
    if (hashSet.hashCode() != entrySet.hashCode()) {
        throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
    }
}
 

import java.util.Set; //导入方法依赖的package包/类
public static void main(String[] args) throws Exception {
    final EnumMap<TestEnum, String> enumMap = new EnumMap<>(TestEnum.class);

    for (TestEnum e : TestEnum.values()) {
        enumMap.put(e, e.name());
    }

    Set<Map.Entry<TestEnum, String>> entrySet = enumMap.entrySet();
    HashSet<Map.Entry<TestEnum, String>> hashSet = new HashSet<>(entrySet);

    if (false == hashSet.equals(entrySet)) {
        throw new RuntimeException("Test FAILED: Sets are not equal.");
    }
    if (hashSet.hashCode() != entrySet.hashCode()) {
        throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
    }
}
 

import java.util.Set; //导入方法依赖的package包/类
@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    Set<TypeLabel> labelSet = this.labelSet;
    result = prime * result + ((labelSet == null) ? 0 : labelSet.hashCode());
    result = prime * result + (this.negated ? 1231 : 1237);
    result = prime * result + this.var.hashCode();
    return result;
}
 

import java.util.Set; //导入方法依赖的package包/类
private static void testSecureSetHashCode() {
    System.out.println("------ SecureSet.hashCode() -----");

    Subject subj = makeSubj(false, false, false);

    // Make sure two other Set types that we know are equal per
    // SecureSet.equals() and verify their hashCodes are also the same
    Set<Principal> equalHashSet = new HashSet<>(Arrays.asList(princVals));

    if (subj.getPrincipals().hashCode() != equalHashSet.hashCode()) {
        throw new RuntimeException(
                "SecureSet and HashSet hashCodes() differ");
    }
    System.out.println("SecureSet.hashCode() tests passed");
}