浅谈Java中hashCode的正确求值方法

public class HashCodeDemo {
  static class HashCodeClass {
    private final boolean bResult;
    private final byte byteValue;
    private final char charValue;
    private final short shortValue;
    private final int intValue;
    private final long longValue;
    private final float floatValue;
    private final double doubleValue;
    private final String str;
    private final int[] arrayValue;

    //volatile表示每次均在内存中去存取该变量，以保证该变量是最新的
    private volatile int hashCode;

    public HashCodeClass() {
      bResult = false;
      byteValue = 1;
      charValue = 'a';
      shortValue = 1;
      intValue = 1;
      longValue = 1l;
      floatValue = 1.0f;
      doubleValue = 1.0d;
      str = getClass().getName();
      arrayValue = new int[] {1,2,3,4,5};
    }

    @Override
    public int hashCode() {
      if(hashCode == 0) {
        // 设置一个非零的初始值，可以增加零域的冲突性
        int result = 17;
        // 如果省略乘数，那么只是字母顺序不同的所有字符串都会有相同的散列码
        final int HASH_CODE = 31;
        result = HASH_CODE * result + (bResult ? 1 : 0);
        result = HASH_CODE * result + byteValue;
        result = HASH_CODE * result + charValue;
        result = HASH_CODE * result + shortValue;
        result = HASH_CODE * result + intValue;
        result = HASH_CODE * result + (int) (longValue ^ (longValue >>> 32));
        result = HASH_CODE * result + Float.floatToIntBits(floatValue);
        long doubleLongValue = Double.doubleToLongBits(doubleValue);
        result = HASH_CODE * result + (int) (doubleLongValue ^ (doubleLongValue >>> 32));
        result = HASH_CODE * result + (str == null ? 0 : str.hashCode());
        System.out.println("str=" + str + ", str.hashCode=" + str.hashCode());
        result = HASH_CODE * result + arrayValue.hashCode();
        return result;
      } 
      return hashCode;
    }
  }

  public static void main(String[] args) {
    HashCodeClass obj = new HashCodeClass();
    System.out.println("obj.hashCode=" + obj.hashCode());
    System.out.println("obj="+obj.toString());
  }
}

str=com.demo.test.HashCodeDemo$HashCodeClass, str.hashCode=-205823051
obj.hashCode=946611167
str=com.demo.test.HashCodeDemo$HashCodeClass, str.hashCode=-205823051
obj=com.demo.test.HashCodeDemo$HashCodeClass@386c23df