Java tips

Archived

This page has been archived and will receive no further updates.

sources:

Java All-In One Desk Reference For Dummies, Second Edition

getters and setters

don’t make variables in a class public. if you need the variable to be publicly accessible, create a get method:

public Object getVar() {
    return var;
}

if you need the variable to be publicly modifiable, create a set method:

public Object setVar(Object myVar) {
    var = myVar;
}

preventing instantiation of a class

create a private constructor that does nothing:

public class MyClass {
    private MyClass() {}
}

template for equals method:

public boolean equals(Object obj) {
    // an object must equal itself
    if (this == obj)
        return true;

    // no object equals null
    if (this == null)
        return false;

    // objects of different types are never equal
    if (this.getClass() != obj.getClass())
        return false;

    // cast to an Employee, then compare the fields
    Employee emp = (Employee) obj;
    return this.lastName.equals(emp.getLastName())
        && this.firstName.equals(emp.getFirstName());
}

(source: http://media.wiley.com/product_ancillary/12/04701245/DOWNLOAD/Java_AIO_code_files.zip)

random number generator:

int low = 1;      // the lowest value in the range
int high = 6;     // the highest value in the range
int rnd = (int)(Math.random() * (high - low + 1)) + low;

(source: Java All-In One Desk Reference For Dummies, Second Edition, p.136)

class constructors

class constructors can call other class constructors using the this keyword

this can only be used in the very first statement of the constructor

Ex:

public class MyClass {
    public MyClass(int first, int second) {
        // do something
    }

    public MyClass(int first, int second, int third) {
        this(first, second);
        third = ...
    }
}

My wiki