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javac++pointersstructtranslation
menemenemu
menemenemu

Reputation: 209

translate c++ code into java

I need to translate some c++ into java, but I have I few issues.

How to I have to deal with pointers when they are declared as arguments in the Method?

static void test( double *output){}

Also what is and how can I replace struct?

struct test { int t;
int arg;
float *pva;
double *array;
}

And then in the code they use:

double test(struct test *test)
{}

Oh and a last one.. this is also inside struct test, what means :

test->arg

Upvotes: 0

Views: 691

Answers (4)

Giorgio
Giorgio

Reputation: 5173

You do not have pointers in Java, only references and only for objects (not for primitive types). References are like pointers, but you use the '.' notation instead of '*' or '->'. Also, you do not need to delete objects in Java, you just stop using them and eventually the garbage collector with destroy them.

Answering your points above, from bottom to top: If test is a pointer to a struct or class in C++, and arg is a member variable of test, then

test->arg

is used to access the member through the pointer. This would map to

test.arg

in Java, if arg is a public member variable of the test object.

I would translate the following:

struct test
{
    int t;
    int arg;
    float *pva;
    double *array;
}

...

double test(struct test *test)
{}

to

public class Test
{
    public int t;

    public int arg;

    float [] pva;

    double [] array;
}

...

public static double test(Test test)
{}

For the first case, i.e. the function

static void test( double *output){}

you cannot pass a pointer to double and modify the double in Java. You have to return a double. If you need the double also as an input parameter, you specify it as a normal parameter that is passed by value:

static double test(double output)
{}

I hope this helps.

Upvotes: 1

Luchian Grigore
Luchian Grigore

Reputation: 258568

static void test( double *output){}

This needs more context, it can mean a pointer to a double or an array of doubles. 

struct test { int t;
int arg;
float *pva;
double *array;
}

A struct is a class with default public access level. You can replace it with a class with public members.

test->arg

This accesses the arg member in test.

Upvotes: 1

iammilind
iammilind

Reputation: 69988

(1) static void test( double *output){}

Here double* can be replaced with a Double[] (assume that you do a new Double[]) and the method can be put inside a class.

class testMethod {
  public static void test (Double []output) { }
}

(2) how can I replace struct? It can be replaced with a class.

class test {
public int t;
public int arg;
public Float []pva;
public Double []array;
}

(3) double test(struct test *test) {} It can be,

double test (test t) {}

(4) test->arg

Java doesn't have pointers (though it's implemented with reference); so above statement will be test.arg

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533492

In the simple cases you can replace float * and double * with float [] and double [] However C++ allows you to do all sorts of unpleasant things which are difficult to translate into Java because it is not allowed in Java.

You can replace a struct with a class

If you want to understand basic C++ syntax, I suggest you read a guide on how to program in C++.

Upvotes: 0

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