Java tutorial
/**
@version 1.10 1997-07-01
@author Cay Horstmann
*/
#include"Printf4.h"#include<string.h>#include<stdlib.h>#include<float.h>
/**
@param format a string containing a printf format specifier
(such as "%8.2f"). Substrings "%%" are skipped.
@return a pointer to the format specifier (skipping the '%')
or NULL if there wasn't a unique format specifier
*/
char*find_format(const char format[]){char*p;char*q;
p=strchr(format,'%');while(p!=NULL&&*(p+1)=='%') /* skip %% */
p=strchr(p+2,'%');if(p==NULL)return NULL;
/* now check that % is unique */
p++;q=strchr(p,'%');while(q!=NULL&&*(q+1)=='%') /* skip %% */
q=strchr(q+2,'%');if(q!=NULL)return NULL; /* % not unique */
q=p+strspn(p," -0+#"); /* skip past flags */
q+=strspn(q,"0123456789"); /* skip past field width */
if(*q=='.'){q++;q+=strspn(q,"0123456789");}
/* skip past precision */
if(strchr("eEfFgG",*q)==NULL)return NULL;
/* not a floating-point format */
return p;}
JNIEXPORT void JNICALL Java_Printf4_fprint(JNIEnv*env,jclass cl,jobject out,jstring format,jdouble x){const char*cformat;char*fmt;jclass class_PrintWriter;jmethodID id_print;char*cstr;int width;int i;
if(format==NULL){(*env)->ThrowNew(env,(*env)->FindClass(env,"java/lang/NullPointerException"),"Printf4.fprint: format is null");return;}
cformat=(*env)->GetStringUTFChars(env,format,NULL);fmt=find_format(cformat);
if(fmt==NULL){(*env)->ThrowNew(env,(*env)->FindClass(env,"java/lang/IllegalArgumentException"),"Printf4.fprint: format is invalid");return;}
width=atoi(fmt);if(width==0)width=DBL_DIG+10;cstr=(char*)malloc(strlen(cformat)+width);
if(cstr==NULL){(*env)->ThrowNew(env,(*env)->FindClass(env,"java/lang/OutOfMemoryError"),"Printf4.fprint: malloc failed");return;}
sprintf(cstr,cformat,x);
(*env)->ReleaseStringUTFChars(env,format,cformat);
/* now call ps.print(str) */
/* get the class */
class_PrintWriter=(*env)->GetObjectClass(env,out);
/* get the method ID */
id_print=(*env)->GetMethodID(env,class_PrintWriter,"print","(C)V");
/* call the method */
for(i=0;cstr[i]!=0&&!(*env)->ExceptionOccurred(env);i++)(*env)->CallVoidMethod(env,out,id_print,cstr[i]);
free(cstr);}
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.io.*;
/**
* @version 1.10 1997-07-01
* @author Cay Horstmann
*/
class Printf4 {
public static native void fprint(PrintWriter ps, String format, double x);
static {
System.loadLibrary("Printf4");
}
}
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.io.*;
/**
* @version 1.10 1997-07-01
* @author Cay Horstmann
*/
class Printf4Test {
public static void main(String[] args) {
double price = 44.95;
double tax = 7.75;
double amountDue = price * (1 + tax / 100);
PrintWriter out = new PrintWriter(System.out);
/* This call will throw an exception--note the %% */
Printf4.fprint(out, "Amount due = %%8.2f\n", amountDue);
out.flush();
}
}