Tips and tricks

1. Tricks on immutability

a. Always make a copy of mutable objects inside your methods, e.g.

void myMethod(Date date) {
 Date myCopy = new Date(date.getTime());
}

b. How do I create an immutable Java Bean or POJO? Make it read-only, and pass any parameters during initialisation (in the constructor):

public class MyClass {
private int param1;
private String param2;
private Date date;

public MyClass (int param1, String param2, Date d) {
    this.param1 = param1;
    this.param2 = param2;
    this.date = new Date(d.getTime());
}

public int getParam1() {
    return param1;
}

public String getParam2() {
    return param2;
}

public Date getDate() {
    return new Date(date.getTime());
}
}

c. Immutable objects and Hibernate

• set the access type to “field” in order to use reflection to set the fields instead of property access, which uses setters.
  
• set mutable to false (Hibernate will perform small optimizations, too).