How to get 0-padded binary representation of an integer in java?

The "why" and "when" of other methods

Although String.format() might be great when you need fixed numbers of characters, alternate methods have their own value.

If you are working with negative numbers, let the mambo of | and << do the magic:

int len = 16;
int val = -42; // because life is not always positive
String formattedBinary = Integer.toBinaryString((1 << len) | val).substring(1);
System.out.println(formattedBinary); // Output: "1111111111101010"
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But here's a secret from the web developers’ corner: when efficient padding is your top priority, immediately call StringUtils.leftPad() from Apache Commons Lang:

 String binaryString = Integer.toBinaryString(42);
String paddedBinary = StringUtils.leftPad(binaryString, 16, '0');
System.out.println(paddedBinary); // Output: "00000000101010"
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Too posh to push? Roll up your sleeves and customize your own padding using custom loops or Arrays.fill(). Result? The same, but now with 100% more feeling of superiority and 0 external dependencies:

char[] paddingArray = new char[42]; // because now you can
Arrays.fill(paddingArray, '0');
System.arraycopy(Integer.toBinaryString(42).toCharArray(), 0, paddingArray, 42 - Integer.toBinaryString(42).length(), Integer.toBinaryString(42).length());
String paddedBinary = new String(paddingArray);
System.out.println(paddedBinary); // Output: "00000000000000000000000000000000000000000000000101010"
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And remember - always check the string length before padding. Otherwise, your binary string might end up longer than a boring monologue.

Getting your hands dirty with bitwise manipulation

Bitwise operations might sound scarier than a horror movie, but they are your secret weapon to perform incredible tasks.

Working with negative integers? Ensure the very correct sign by smoothly sliding (1 << len) | (val & ((1 << len) - 1)) into your code routine.

The masking operation (val & ((1 << len) - 1)) is more than a masquerade – it is a mask that lets only len bits pass through it, clipping the integer to the permitted length.

The dynamic lengths are no more a mystery. To stay adaptive, just shift 1 left by len bits. It will create a binary string of ones, and hence, make you the master of padding techniques.