Java tips

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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 = ...
    }
}