如何在Java中通过指针算法访问数组元素

Question

Given the following declaration in C, I can apply '+' to the address, and access other elements.

char toto[5];

In other words, applying this operator +

toto+0x04

Accesses a different array element in Java.

Is there another way to implement this operation in java ?

Many Thanks

Answer 1

If I'm right you want to access the element at that position in the array. You can do this in java.

char foo[] = new char[]{'1', '2','3','4', '5'};
char fooAtPositionFour = foo[4];

and assign a new value this way:

foo[4] = 'x';

Answer 2

Technically no since toto+4 is an address and Java's memory management policy is quite different from C's one. However you can get *(toto+4) with toto[4] ;)

Answer 3

in fact i need to isolate the last four byte where param is a char[]

Do you need the last four bytes, or the last char? The last char then toto[toto.length-1]

For the last four bytes you would need to turn the char array (UTF-16 in Java, I've no idea what the encoding would be in C) into a byte array then take the last four bytes.

new String(toto).toBytes("THE_CHAR_ENCODING_YOU_WANT_TO_USE")

Answer 4

Almost always there is another way in java to implement what you want.

You rarely process char[] directly. Using String and StringBuilder is preferred.

String toto = "hello";
String lastChar = toto.substring(4); // from the 4th character.

To answer your question literally. You can use the sun.misc.Unsafe with get/putByte or get/putChar class to do pointer arithmetic, but I suggest avoiding it unless you really, really need to.