hashcode

I have below class. Request.java public class Request implements Serializable { private String id; private String name; private String hid; // getters and setters // This class does not override any equals() and hashCode() methods } public class EmpRequest implements Serializable { private Request request; //Now here in this class I need override equals() and hashCode() methods based on **request** } In EmpRequest class, I need to override equals() and hashCode() based on properties of Request object. If two request objects id is equal then i need to return true . If two objects ids are not

I've been reading documentation about String.hashCode() on http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/String.java Trying obtain an identical result from an identical string, but I did not come up with any satisfying results. In Objective-C [NSString hash] gives a totally different result. Have anyone already done this? Thanks The answer provided by Alfred is not correct. First of all, hashCode can return negative, so the return type should be a signed integer and not an unsigned integer. Secondly, the charAsciiValue++ is off. In the original Java

运用equals来比对对象或者是对象集合的removeAll等是需要重写equals和hashCode，IDEA重写equals和hashCode 1、equals 对于String和Integer等包装类而言，比较的是堆中的值。 对于自定义的普通类，equals比较的是内存的首址，比较两边指向是不是同一个对象。 注意：== 比较的也是内存的首址。 a、如果用==来比较String类型就比较特殊了，对于String="a"这种赋值的，两个相同的值用==比较也是相同的，但是如果是new String()出来的用==比较就不相同了。因为对于赋值的，java会检查堆中是否有相同的值，如果有则新对象和老对象的地址都是该值在堆中的地址；new String()开辟的就是两个栈了，用==比较就不同了。 b、对于包装类，比如Integer，进行自动装箱操作，如果数值在-128~127则会有缓存，==是相同的；如果数值不在那个范围，则不同。 2、用equals比较对象需要重写equals和hashCode 当equals被重写时，通常有必要重写hashCode，以维护hashCode的常规协定（该协定声明相等对象必须具有相等的哈希码）。 hashCode用于散列数据的快速存取，如果用HashSet/HashMap/Hashtable类来存储数据时