JAVA Cheat Sheet

A Programming › Java cheat sheet in English by pca221

17,777 views 3,604 downloads 9 Sep 2016 History

PRs

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Data Types

byte	8 bits	-2^{7 to 2}7 - 1
short	16 bits	-2^{15 to 2}15 - 1
int	32 bits	-2^{31 to 2}31 - 1
long	64 bits	-2^{63 to 2}63 - 1
boolean	true \ false
char	16 bit unicode	-2^{15 to 2}15 - 1
float	32 bit decimal	-2^{31 to 2}31 - 1
double	64 bit decimal	-2^{63 to 2}63 - 1

Encapsulation

public	user can see
private	hide from user

Swap

int temp = e1;
e1 = e2;
e2 = temp;

While loop

while(condition) {
//codes
}

For Loop Array

string word = "Hello";
for (char c: word.toCharArray()){
     system.out.println()
     ...
}

Class

public class ABCD {
     public A () {
          //codes
     }
     public void B() {
          //codes
     }
}




*public A = default, run automatic
*public void B = need call

Commands

\n	new line
\t	tab
\"	"
\'	'
\\	\

Do - While loop

do {
   //codes
} while (condition);

For Loop List

int mylist = {100,200,300,400};
for(int item = 0; item< mylist.length; iterm++){
  //codes
}

for(int item mylist) {
  //codes
}

Abbreviation

JVM	JAVA Virtual Machine
JRE	JAVA Runtime Environment
JDK	JAVA Development Kit
bytecode	intermediate level long
compiler	JAVA -> Bytecode
Java Runtime	bytecode -> machine
native compiler	directly to machine

Array

int[] mylist = new int[2]
mylist[0] = 100;
mylist[1] = 200;

int[] mylist = {100, 200}

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