C/Unix quick translation to Java language

/* C */	// Java	//comment
#include <stdio.h> int main(int argc, char *argv[ ]) { printf("Hello, World\n"); }	import java.io.; import java.lang.; public class hello { public static void main(String[ ] argv) throws IOException { int argc=argv.length; System.out.print("Hello, World\n"); System.out.close(); } }	1. Save this in a text file called "hello.java". 2. Java "class hello" name must match source text file name "hello.java". 3. This is a java "application" not "applet". 4. int argc=argv.length; //not "length()"! 5. Alternate: System.out.println("Hello, World"); 6. "throws IOException" needed for file i/o processing. 7. Can also use: "Exception" instead of "IOException".
gcc hello.c -o hello.exe	javac hello.java	javac: compiles "hello.java" into "hello.class".
./hello.exe	java hello	java: virtual machine interpreter (JVM). passing 3 arguments: "java hello x y z" Arguments offset by one: C argv[1] equals Java argv[0] reading from stdin (System.in.read()): "java hello <file.txt"

int i, n;
int i, n;
32 bit signed integer

int *a; int [ ] a; pointer = object reference

int a[10];
//no static or stack allocation

int *a = (int*)malloc(10*sizeof(int));
int [ ] a = new int[10];
dynamic allocation

n=a[ i ];
n=a[ i ]; //can't do this with String class

a[ i ]=n;
a[ i ]=n; //can't do this with String class

#define N 10 /* preprocessor */
n = a.length;
size of an array (e.g. 10).

const int i = 64;
final int i = 64;
//public static final int i = 64;

signed char cs; i=cs;
byte cs; i=cs;
java: 8 bit signed integer

unsigned char cu; i=cu;
byte cu; i=0xff & cu;
java: does not support unsigned arithmetic

short i =32767;
short i = 32767;
java: 16 bit signed integer

int i = 2147483647;
int i = 2147483647;
java: 32 bit signed integer;

long i = 9223372036854775807L;
long i = 9223372036854775807L;
java: 64 bit signed integer;

float f =3.4e+38; float f =3.4e+38; java: 32 bit IEEE 754 float

double d = 1.8e+308;
double d = 1.8e+308;
java: 64 bit IEEE 754 float

long double dd= 1.2e4932;

java: none

int i=0;
boolean b=false;
java integers are NOT boolean logic.

int i=1; /* i!=0 */
boolean b=true;
c negative and positive numbers are true logic.

if (i) { } else { }
if (i!=0) { } else { }
if (b) { } else { }

n=i?1:0;
n=(i!=0)?1:0;
n=b?1:0;

if (i && n) { }
if ((i!=0) && (n!=0)) { }
logical AND

if (i || n) { }
if ((i!=0) || (n!=0)) { }
logical OR

char c;
char c;
java: 16 bit Unicode character

char c; c=i;
c=(char)i;
javac compiler error without cast

#include <ctype.h>
if (isalpha(c)) { }
import java.lang.*;
if (Character.isLetter(c)) { }
import java.lang.Character;
if (java.lang.Character.isLetter(c)) { }

if (isupper(c)) { }
if (Character.isUpper(c)) { }

if (islower(c)) { }
if (Character.isLower(c)) { }

if (isdigit(c)) { }
if (Character.isDigit(c)) { }
java handles international digits

if (isxdigit(c)) { }
if (Character.digit(c,16)>=0 && Character.digit(c,16)<16) { }

if (isalnum(c)) { }
if (Character.isLetterOrDigit(c)) { }

if (isspace(c)) { }
if (Character.isWhiteSpace(c)) { }

if (iscntrl(c)) { }
if (Character.isISOControl(c) { }

c = toupper(c);
c = toUpperCase(c);

c = tolower(c);
c = toLowerCase(c);

#include <strings.h>
char s[ ] ; //array of char's
import java.lang.*;
String s; //an "immutable" class import java.lang.String;
import java.lang.StringBuffer;
StringBuffer s; //"mutable" class

char s[ ]="abc"; String s="abc"; StringBuffer sb=new StringBuffer("abc");

char s[10];
//can't do this with String class StringBuffer sb=new StringBuffer(10);

char s[10]="abc";
//can't do this with String class

char s[ ] = { 'a', 'b', 'c', 0 }; String s=new String(new char [ ] { 'a', 'b', 'c' } );
StringBuffer sb
=new StringBuffer(new String(new char [ ] { 'a', 'b', 'c' } ));

char *s, *t;
String s, t;

s = t;
s = t;
copy reference pointer only

strcpy(s, t); s=t.clone();
s=new String(t); //alternate
s=tb.toString();
sb.delete(0,sb.length()).append(tb);

strcpy(s, t+i); s=t.substring( i ); sb.delete(0,sb.length()).append(t,i,t.length());

strcat(s, "def"); s+="def"; //String class creates new instance sb.append("def"); s+=sb;

i=strlen(s); i=s.length( );
i=sb.length();

c=s[ i ]; c=s.charAt( i ); c=sb.charAt( i );

s[ i ]=c;
s=s.substring(0, i)+c+s.subtring(i+1);
sb.setCharAt( i, c);

if (!strcmp(s, "abc")) { break; }
if (s.equals("abc")) { break; }
if (s.compareTo("abc")==0) { break; }

if ( s == t ) { break; }
if ( s == t ) { break; }
compare reference pointer only

if (strcmp(s, t)>0)) { break; }
if (s.compareTo(t)>0) { break; }
s is greater than t

if (strcmp(s, t)<0)) { break; }
if (s.compareTo(t)<0) { break; }
s is less than t

sscanf(s, "%d", &i); i=atoi(s); i=Integer.parseInt( s );
import java.lang.Integer;

sscanf(s, "%x", &i);
i=Integer.parseInt( s, 16); #include <stdio.h>

sscanf(s, "%o", &i); i=Integer.parseInt( s, 8);

sscanf(s, "%f", &f); f=atof(s);
f=Float.parseFloat(s);
import java.lang.Float;

sscanf(s, "%g", &d);
d=Double.parseDouble(s);
import java.lang.Double;

i=strtol(s, 0, base); i=Integer.parseInt( s, base);

sprintf(s, "%d", i);
s=Integer.toString(i);
s=String.valueOf( i ); //base 10 only

sprintf(s, "%x", i);
s=Integer.toHexString(i); s=Integer.toString(i, 16);

sprintf(s, "%o", i);
s=Integer.toOctalString(i);
s=Integer.toString(i, 8);

sprintf(s, "%f", f);
s=Float.toString( f );
s=String.valueOf( f );

#include <stdio.h>
printf("Hello World\n"); import java.lang.*;
System.out.print("Hello, World\n");
import java.lang.System;
System.out.println("Hello, World");

printf("i=%d\n", i);
System.out.print("i="+i+"\n");
java.lang.System.out.println("i="+i);

printf("f=%f\n", f);
System.out.print("f="+f+"\n");
uses PrintStream class

fprintf(stderr, "error msg\n");
System.err.print("error msg\n");

c=getchar( ); c=getc(stdin);
int c; c=System.in.read( ); EOF=-1; uses InputStream class

putchar(c); putc(c, stdout);
int c='A'; System.out.write(c); //outputs "A"
System.out.print(c); //outputs "65"
System.out.print((char)c); //="A"

putc(c, stderr);
System.err.write(c);

exit(1);
System.err.close();
System.out.close();
System.exit(1);
import java.lang.System;

#include <stdio.h>
FILE fout; //stream version
import java.io.*;
PrintStream fout = null; //text base output
Binary files: DataOutputStream
can't use abstract class: OutputStream
NOT for random access files

if (!(fout=fopen(fn, "w")) {
fprintf(stderr, "fopen error: %s\n", fn); }
try {
fout = new PrintStream(new FileOutputStream(fn));
}
catch (Exception e) {
System.err.println ("PrintStream("+fn+") "+e);
System.err.close( ); System.exit(1); }
java does not "flush"
and "close" files upon exit

fprintf(fout, "i=%d\n", i);
fout.println("i="+i);
http://www.javacamp.org/javavscsharp/

fprintf(fout, "%d", i);
fout.print( i );
PrintStream

fprintf(fout, "%f", f);
fout.print( f );
PrintStream

fprintf(fout, "%s", s);
fout.print( s );
PrintStream

fprintf(fout, "%c", i);
fout.printf((char)i);
treat integer as character

putc(c, fout); fputc(c, fout); fout.write(c); OutputStream, PrintStream; int c; must cast

fflush(fout);
fout.flush( );
OutputStream, PrintStream

fclose(fout);
fout.close();
OutputStream, PrintStream

#include <stdio.h>
FILE fin; //stream version
import java.io.*;
DataInputStream fin=null;
Binary files: DataInputStream
NOT for random access files
can't abstract class: InputStream

if (!(fin=fopen(fn, "r")) {
fprintf(stderr, "fopen error: %s\n", fn); } try {
fin = new DataInputStream(new FileInputStream(fn));
}
catch (Exception e) {
   System.err.println ("DataInputStream("+fn+") "+e);
   System.err.close( ); System.exit(1); } java does not "flush"
and "close" files upon exit

Internet file reading
import java.net.*;

try   {
fin = new DataInputStream((new URL(fn)).openStream());
}
catch (Exception e) {
System.err.println("DataInputStream("+fn+") "+e);
System.err.close( ); System.exit(1);
}
import java.net.URL;
Examples:
fn="http:// bear.ces.cwru.edu/ index.html";

or

fn="file:// /home /users /wolff /EECS382 /JAVA /testj.java";

c=getc(fin); c=fgetc(fin);
int c; c=fin.read( );
8-bit ascii; EOF=-1;

fgets(s, n, fin);
int c; s=""; c=fin.read();
for(i=0; i<n && c>=0; i++) { s+=(char)c; fin.read(); }
n is optional since
java strings are unlimited.

fclose(fin);
fin.close( );
InputStream, DataInputStream

#include <stdio.h>
FILE fp; //Random access
import java.io.*;
RandomAccessFile fp = null;
import java.io.RandomAccessFile;

if (!(fp=fopen(fn, "rw")) {
fprintf(stderr, "fopen error: %s\n", fn); } try { fp = new RandomAccessFile(fn, "rw"); }
catch (Exception e) {
System.err.println("RandomAccessFile("+fn+") "+e);
System.err.close( ); System.exit(1); }
java requires "rw" for write and "r" for read.

puts(s, fp);
fp.writeBytes(s);
8-bit ascii characters; Uni-code also.

putc(c, fp);
fp.write(c);
always works; 8-bit ascii characters; int c;

int c; c=getc(fp);
c=fp.read( );
EOF = -1

fgets(s, n, fp);
s=fp.readLine( );
rewrite using read()

fseek(fp, offset, SEEK_SET);
fp.seek(offset);
from beginning of file

offset=ftell(fp);
offset=fp.getFilePointer( );

fseek(fp,0,SEEK_END); n=ftell(fp);
n=fp.length();
size of file

fclose(fp); fp.close( );

#include <stdio.h>
#include <ctype.h>
#include <strings.h>

int main(int argc, char *argv[ ]) {
int i, c;
int uflag=0, fflag=0;
char *fn=0;
FILE *fin=0;

/* argv[0]=program */
for(i=1; i<argc; i++) {
    if (!strcmp(argv[i], "-U")) { uflag=1; }
    else if (argv[i][0] != '-') { fflag=1; fn=strdup(argv[i]); }
    else {
      fprintf(stderr, "cat: unknown flag=%s\n", argv[i]);
      exit(1);
} }
if (fflag) {
    fin = fopen(fn, "r");
    if (!fin) {
      fprintf(stderr, "fopen(%s) error\n", fn);
      exit(1);
} }
for(;;) {
    c=(fflag)?fgetc(fin):getchar();
    if (c==EOF) { break; }
    if (uflag) { c=toupper(c); }
    putchar(c);
}
if (fflag) { fclose(fin); }
}

import java.lang.*;
import java.io.*;

public class cat {

public static void main(String[ ] argv) throws IOException {
    int i, c, argc=argv.length;
    boolean uflag=false, fflag=false;;
    String fn = null;
    DataInputStream fin = null;

    for(i=0; i<argc; i++) {
    if (argv[i].equals("-U")) { uflag=true; }
    else if (argv[i].charAt(0) != '-') { fflag=true; fn=new String(argv[i]); }
    else {
    System.err.println("cat: unknown flag="+argv[i]);
    System.err.close();
    System.exit(1);
    } }
    if (fflag) {
    try {
    fin = new DataInputStream(new FileInputStream(fn));
    }
      catch (Exception e) {
    System.err.println ("DataInputStream("+fn+") "+e);
    System.err.close( ); System.exit(1);
    } }
    for(;;) {
      c=(fflag)?fin.read():System.in.read();
    if (c<0) { break; }
    if (uflag) { c=Character.toUpperCase((char)c); }
    System.out.write(c);
    }
    if (fflag) { fin.close(); }
}
}

Example: "wcat.java" program (compiled version: wcat.class)

Read a file from command line, standard in or the web. Optional flag -U translates file to uppercase:

0. "javac wcat.java"
1. "java wcat <file.txt"
2. "java wcat -U <file.txt"
3. "java wcat file.txt"
4. "java wcat -U file.txt"

"Copyright 2005.05.26 by Francis G. Wolff, fxw12@case.edu"
version 1.0
additional contributions and corrections welcomed!

int i, n;	int i, n;	32 bit signed integer
int *a;	int [ ] a;	pointer = object reference
int a[10];	//no static or stack allocation
int a = (int)malloc(10*sizeof(int));	int [ ] a = new int[10];	dynamic allocation
n=a[ i ];	n=a[ i ];	//can't do this with String class
a[ i ]=n;	a[ i ]=n;	//can't do this with String class
#define N 10 /* preprocessor */	n = a.length;	size of an array (e.g. 10).
const int i = 64;	final int i = 64;	//public static final int i = 64;
signed char cs; i=cs;	byte cs; i=cs;	java: 8 bit signed integer
unsigned char cu; i=cu;	byte cu; i=0xff & cu;	java: does not support unsigned arithmetic
short i =32767;	short i = 32767;	java: 16 bit signed integer
int i = 2147483647;	int i = 2147483647;	java: 32 bit signed integer;
long i = 9223372036854775807L;	long i = 9223372036854775807L;	java: 64 bit signed integer;
float f =3.4e+38;	float f =3.4e+38;	java: 32 bit IEEE 754 float
double d = 1.8e+308;	double d = 1.8e+308;	java: 64 bit IEEE 754 float
long double dd= 1.2e4932;		java: none

int i=0;	boolean b=false;	java integers are NOT boolean logic.
int i=1; /* i!=0 */	boolean b=true;	c negative and positive numbers are true logic.
if (i) { } else { }	if (i!=0) { } else { }	if (b) { } else { }
n=i?1:0;	n=(i!=0)?1:0;	n=b?1:0;
if (i && n) { }	if ((i!=0) && (n!=0)) { }	logical AND
if (i \|\| n) { }	if ((i!=0) \|\| (n!=0)) { }	logical OR

char c;	char c;	java: 16 bit Unicode character
char c; c=i;	c=(char)i;	javac compiler error without cast
#include <ctype.h> if (isalpha(c)) { }	import java.lang.*; if (Character.isLetter(c)) { }	import java.lang.Character; if (java.lang.Character.isLetter(c)) { }
if (isupper(c)) { }	if (Character.isUpper(c)) { }
if (islower(c)) { }	if (Character.isLower(c)) { }
if (isdigit(c)) { }	if (Character.isDigit(c)) { }	java handles international digits
if (isxdigit(c)) { }	if (Character.digit(c,16)>=0 && Character.digit(c,16)<16) { }
if (isalnum(c)) { }	if (Character.isLetterOrDigit(c)) { }
if (isspace(c)) { }	if (Character.isWhiteSpace(c)) { }
if (iscntrl(c)) { }	if (Character.isISOControl(c) { }
c = toupper(c);	c = toUpperCase(c);
c = tolower(c);	c = toLowerCase(c);

#include <strings.h> char s[ ] ; //array of char's	import java.lang.*; String s; //an "immutable" class	import java.lang.String; import java.lang.StringBuffer; StringBuffer s; //"mutable" class
char s[ ]="abc";	String s="abc";	StringBuffer sb=new StringBuffer("abc");
char s[10];	//can't do this with String class	StringBuffer sb=new StringBuffer(10);
char s[10]="abc";	//can't do this with String class
char s[ ] = { 'a', 'b', 'c', 0 };	String s=new String(new char [ ] { 'a', 'b', 'c' } );	StringBuffer sb =new StringBuffer(new String(new char [ ] { 'a', 'b', 'c' } ));
char s, t;	String s, t;
s = t;	s = t;	copy reference pointer only
strcpy(s, t);	s=t.clone(); s=new String(t); //alternate	s=tb.toString(); sb.delete(0,sb.length()).append(tb);
strcpy(s, t+i);	s=t.substring( i );	sb.delete(0,sb.length()).append(t,i,t.length());
strcat(s, "def");	s+="def"; //String class creates new instance	sb.append("def"); s+=sb;
i=strlen(s);	i=s.length( );	i=sb.length();
c=s[ i ];	c=s.charAt( i );	c=sb.charAt( i );
s[ i ]=c;	s=s.substring(0, i)+c+s.subtring(i+1);	sb.setCharAt( i, c);
if (!strcmp(s, "abc")) { break; }	if (s.equals("abc")) { break; }	if (s.compareTo("abc")==0) { break; }
if ( s == t ) { break; }	if ( s == t ) { break; }	compare reference pointer only
if (strcmp(s, t)>0)) { break; }	if (s.compareTo(t)>0) { break; }	s is greater than t
if (strcmp(s, t)<0)) { break; }	if (s.compareTo(t)<0) { break; }	s is less than t
sscanf(s, "%d", &i); i=atoi(s);	i=Integer.parseInt( s );	import java.lang.Integer;
sscanf(s, "%x", &i);	i=Integer.parseInt( s, 16);	#include <stdio.h>
sscanf(s, "%o", &i);	i=Integer.parseInt( s, 8);
sscanf(s, "%f", &f); f=atof(s);	f=Float.parseFloat(s);	import java.lang.Float;
sscanf(s, "%g", &d);	d=Double.parseDouble(s);	import java.lang.Double;
i=strtol(s, 0, base);	i=Integer.parseInt( s, base);
sprintf(s, "%d", i);	s=Integer.toString(i);	s=String.valueOf( i ); //base 10 only
sprintf(s, "%x", i);	s=Integer.toHexString(i);	s=Integer.toString(i, 16);
sprintf(s, "%o", i);	s=Integer.toOctalString(i);	s=Integer.toString(i, 8);
sprintf(s, "%f", f);	s=Float.toString( f );	s=String.valueOf( f );

#include <stdio.h> printf("Hello World\n");	import java.lang.*; System.out.print("Hello, World\n");	import java.lang.System; System.out.println("Hello, World");
printf("i=%d\n", i);	System.out.print("i="+i+"\n");	java.lang.System.out.println("i="+i);
printf("f=%f\n", f);	System.out.print("f="+f+"\n");	uses PrintStream class
fprintf(stderr, "error msg\n");	System.err.print("error msg\n");
c=getchar( ); c=getc(stdin);	int c; c=System.in.read( );	EOF=-1; uses InputStream class
putchar(c); putc(c, stdout);	int c='A'; System.out.write(c); //outputs "A"	System.out.print(c); //outputs "65" System.out.print((char)c); //="A"
putc(c, stderr);	System.err.write(c);
exit(1);	System.err.close(); System.out.close(); System.exit(1);	import java.lang.System;

#include <stdio.h> FILE fout; //stream version	import java.io.*; PrintStream fout = null; //text base output	Binary files: DataOutputStream can't use abstract class: OutputStream NOT for random access files
if (!(fout=fopen(fn, "w")) { fprintf(stderr, "fopen error: %s\n", fn); }	try { fout = new PrintStream(new FileOutputStream(fn)); } catch (Exception e) { System.err.println ("PrintStream("+fn+") "+e); System.err.close( ); System.exit(1); }	java does not "flush" and "close" files upon exit
fprintf(fout, "i=%d\n", i);	fout.println("i="+i);	http://www.javacamp.org/javavscsharp/
fprintf(fout, "%d", i);	fout.print( i );	PrintStream
fprintf(fout, "%f", f);	fout.print( f );	PrintStream
fprintf(fout, "%s", s);	fout.print( s );	PrintStream
fprintf(fout, "%c", i);	fout.printf((char)i);	treat integer as character
putc(c, fout); fputc(c, fout);	fout.write(c);	OutputStream, PrintStream; int c; must cast
fflush(fout);	fout.flush( );	OutputStream, PrintStream
fclose(fout);	fout.close();	OutputStream, PrintStream

#include <stdio.h> FILE fin; //stream version	import java.io.*; DataInputStream fin=null;	Binary files: DataInputStream NOT for random access files can't abstract class: InputStream
if (!(fin=fopen(fn, "r")) { fprintf(stderr, "fopen error: %s\n", fn); }	try { fin = new DataInputStream(new FileInputStream(fn)); } catch (Exception e) { System.err.println ("DataInputStream("+fn+") "+e); System.err.close( ); System.exit(1); }	java does not "flush" and "close" files upon exit
Internet file reading	import java.net.*; try { fin = new DataInputStream((new URL(fn)).openStream()); } catch (Exception e) { System.err.println("DataInputStream("+fn+") "+e); System.err.close( ); System.exit(1); }	import java.net.URL; Examples: fn="http:// bear.ces.cwru.edu/ index.html"; or fn="file:// /home /users /wolff /EECS382 /JAVA /testj.java";
c=getc(fin); c=fgetc(fin);	int c; c=fin.read( );	8-bit ascii; EOF=-1;
fgets(s, n, fin);	int c; s=""; c=fin.read(); for(i=0; i<n && c>=0; i++) { s+=(char)c; fin.read(); }	n is optional since java strings are unlimited.
fclose(fin);	fin.close( );	InputStream, DataInputStream

#include <stdio.h> FILE fp; //Random access	import java.io.*; RandomAccessFile fp = null;	import java.io.RandomAccessFile;
if (!(fp=fopen(fn, "rw")) { fprintf(stderr, "fopen error: %s\n", fn); }	try { fp = new RandomAccessFile(fn, "rw"); } catch (Exception e) { System.err.println("RandomAccessFile("+fn+") "+e); System.err.close( ); System.exit(1); }	java requires "rw" for write and "r" for read.
puts(s, fp);	fp.writeBytes(s);	8-bit ascii characters; Uni-code also.
putc(c, fp);	fp.write(c);	always works; 8-bit ascii characters; int c;
int c; c=getc(fp);	c=fp.read( );	EOF = -1
fgets(s, n, fp);	s=fp.readLine( );	rewrite using read()
fseek(fp, offset, SEEK_SET);	fp.seek(offset);	from beginning of file
offset=ftell(fp);	offset=fp.getFilePointer( );
fseek(fp,0,SEEK_END); n=ftell(fp);	n=fp.length();	size of file
fclose(fp);	fp.close( );