Syntax

Welcome to the syntax page. Post Java syntax you know of here:

Class

class ClassNameIdentifier { 

}

Using access modifiers:

public class ClassNameIdentifier { 

}

private class ClassNameIdentifier { 

}

protected class ClassNameIdentifier { 

}

With inheritance:

class ClassNameIdentifier extends AnotherClass { 

}

NOTE: A class may extend one and only one other class.

Using an interface:

class ClassNameIdentifier implements SomethingInterfaceable { 

}

Or multiple interfaces:

class ClassNameIdentifier implements ThisInterface, ThatInterface{ 

}

And a class that should not be instantiated is abstract:

abstract class ClassNameIdentifier { 

}

A class that canot be extended:

final class ClassName {

}

Method

void methodName() {

}

Using a primitive data type,

int methodName() {
    return 0;
}

Returning an object,

String methodName() {
    return "method return";
}

A public method,

public String methodName() {
    return "method return";
}

A private method,

private String methodName() {
    return "method return";
}

A package-private method,

protected String methodName() {
    return "method return";
}

A method with parameters,

String greet(String userName) {
    return "Hello " + userName;
}

A static method,

static String sayHello() {
    return "Hello";
}

Overriding a method,

@Override
public String toString() {
    return "method return";
}

Calling a Method

methodName();

Calling a static method of a different class,

Math.random();

Calling an object's method (assume it was constructed),

anObject.methodName();

Printing to standard out (console),

System.out.println("insert text here"); //with line return
System.out.print("insert text here too"); //without line return

Variable

Declaring a variable (of type int),

int aWholeNumber;

Initializing a variable,

String userName;
userName = "bob";
double busFare = 4.25;

Declaring an object,

Object anObject;

Constructing an object,

Object anObject = new Object();

Flow Control

When parts of the code are executed on certain conditions or states. Each of these constructs may be nested within one another (see Syntax#Nesting)

Conditional

if(someCondition) {
    //execute when true
}

if(someCondition) {
    //execute when true
} else {
    //execute when false
}

Multiple conditions,

if(someCondition) {
    //execute only this block
    //when someCondition is true
} else if(someOtherCondition) {
    //execute only this block
    //when someOtherCodition is true
} else {
    //execute when all others are false
}

Better scaling multiple conditions,

char singleCharChoice;
switch(singleCharChoice) {
    case 'A':
        //statements if this is case
        break;
    case 'B': case 'b':
        //statements when either case is true
        break;
}

Including a default case,

char singleCharChoice;
switch(singleCharChoice) {
    case 'A':
        //statements if this is case
        break;
    case 'B': case 'b':
        //statements when either case is true
        break;
    default:
        //statements when nothing else holds true
}

Loop

while(someCondition) {
    //statements to repeat
    //make sure you can get out of the loop!
}

When the statements need to execute at least one time,

do {
    //statements to repeat
    //make sure you can get out of the loop!
} while(someCondition);

When the exact number of iterations is known,

for(int i = 0; i < aKnownLimit; i++) {

}

Nesting

do {
    //statements to repeat
    //make sure you can get out of the loop!
    if(aSeparateCondition) {
        //a conditional within a loop!
        while(anotherCondition) {
            //looping within a conditional within a loop!
        }
    }
} while(someCondition);

Package and Imports

To specify a class is a part of a package, the first line in a class file should have a line similar to the following,

package custom.package.path.name;

To import members from other packages, include something similar to the following,

import other.package.path.name.ClassMember;

To import all members within a package, use the character,

import java.util.*;

To import a static method

import static other.package.name.ClassName.methodName

To import an inner class

import other.package.name.ClassName.InnerClassName

External sites

• Java syntax
• Java Keywords