This article shows you five examples to convert a string into a binary string representative or vice verse.

本文向您展示了五个示例，这些示例将字符串转换为二进制字符串表示形式，反之亦然。

Convert String to Binary – Integer.toBinaryString

Convert String to Binary – Bit Masking

Convert Binary to String – Integer.parseInt

Convert Unicode String to Binary.

Convert Binary to Unicode String.

1. Convert String to Binary – Integer.toBinaryString

The steps to convert a string to its binary format.

Convert string to char[].

Loops the char[].

Integer.toBinaryString(aChar) to convert chars to a binary string.

String.format to create padding if need.

package com.mkyong.convert;

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

public class StringToBinaryExample01 {

public static void main(String[] args) {

String input = "Hello";

String result = convertStringToBinary(input);

System.out.println(result);

// pretty print the binary format

System.out.println(prettyBinary(result, 8, " "));

}

public static String convertStringToBinary(String input) {

StringBuilder result = new StringBuilder();

char[] chars = input.toCharArray();

for (char aChar : chars) {

result.append(String.format("%8s", Integer.toBinaryString(aChar)).replaceAll(" ", "0"));// char -> int, auto-cast zero pads

}

return result.toString();

}

public static String prettyBinary(String binary, int blockSize, String separator) {

List result = new ArrayList<>();

int index = 0;

while (index < binary.length()) {

result.add(binary.substring(index, Math.min(index + blockSize, binary.length())));

index += blockSize;

}

return result.stream().collect(Collectors.joining(separator));

}

}

Output

0100100001100101011011000110110001101111

01001000 01100101 01101100 01101100 01101111

2. Convert String to Binary – Bit Masking.

2.1 This Java example will use bit masking technique to generate binary format from an 8-bit byte.

package com.mkyong.convert;

import java.nio.charset.StandardCharsets;

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

public class StringToBinaryExample02 {

public static void main(String[] args) {

String input = "a";

String result = convertByteArraysToBinary(input.getBytes(StandardCharsets.UTF_8));

System.out.println(prettyBinary(result, 8, " "));

}

public static String convertByteArraysToBinary(byte[] input) {

StringBuilder result = new StringBuilder();

for (byte b : input) {

int val = b;

for (int i = 0; i < 8; i++) {

result.append((val & 128) == 0 ? 0 : 1); // 128 = 1000 00000

val <<= 1;

}

}

return result.toString();

}

public static String prettyBinary(String binary, int blockSize, String separator) {

List result = new ArrayList<>();

int index = 0;

while (index < binary.length()) {

result.add(binary.substring(index, Math.min(index + blockSize, binary.length())));

index += blockSize;

}

return result.stream().collect(Collectors.joining(separator));

}

}

Output

01100001

The hard part is this code. The idea is similar to this Java – Convert Integer to Binary using bit masking. In Java, byte is an 8-bit, int is 32-bit, for integer 128 the binary is 1000 0000.

困难的部分是这段代码。这个想法类似于–使用位掩码将整数转换为二进制。在Java中，字节是8位，整数是32位，对于整数128，二进制是1000 0000。

for (byte b : input) {

int val = b; // byte -> int

for (int i = 0; i < 8; i++) {

result.append((val & 128) == 0 ? 0 : 1); // 128 = 1000 0000

val <<= 1; // val = val << 1

}

}

This & is an Bitwise AND operator, only 1 & 1 is 1, other combinations are all 0.

1 & 1 = 1

1 & 0 = 0

0 & 1 = 0

0 & 0 = 0

This val <<= 1 is actually val = val << 1, it is a bit left shift operator, it moves the bits to the left side by 1 bit.

Review the following draft: let’s assume the val is an int, or byte represents a character a.

00000000 | 00000000 | 00000000 | 01100001 # val = a in binary

00000000 | 00000000 | 00000000 | 10000000 # 128

& # bitwise AND

00000000 | 00000000 | 00000000 | 00000000 # (val & 128) == 0 ? 0 : 1, result = 0

00000000 | 00000000 | 00000000 | 11000010 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

& # bitwise AND

00000000 | 00000000 | 00000000 | 10000000 # (val & 128) == 0 ? 0 : 1, result = 1

00000000 | 00000000 | 00000001 | 10000100 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 10000000 # result = 1

00000000 | 00000000 | 00000011 | 00001000 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 00000000 # result = 0

00000000 | 00000000 | 00000110 | 00010000 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 00000000 # result = 0

00000000 | 00000000 | 00001100 | 00100000 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 00000000 # result = 0

00000000 | 00000000 | 00011000 | 01000000 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 00000000 # result = 0

00000000 | 00000000 | 00110000 | 10000000 # val << 1

00000000 | 00000000 | 00000000 | 10000000 # 128

&

00000000 | 00000000 | 00000000 | 10000000 # result = 1

# collect all bits # 01100001

For string a the binary string is 01100001.

3. Convert Binary to String.

In Java, we can use Integer.parseInt(str, 2) to convert a binary string to a string.

package com.mkyong.crypto.bytes;

import java.util.Arrays;

import java.util.stream.Collectors;

public class StringToBinaryExample03 {

public static void main(String[] args) {

String input = "01001000 01100101 01101100 01101100 01101111";

// Java 11 makes life easier

String raw = Arrays.stream(input.split(" "))

.map(binary -> Integer.parseInt(binary, 2))

.map(Character::toString)

.collect(Collectors.joining()); // cut the space

System.out.println(raw);

}

}

4. Convert Unicode String to Binary.

We can use Unicode to represent non-English characters since Java String supports Unicode, we can use the same bit masking technique to convert a Unicode string to a binary string.

由于Java String支持Unicode，因此可以使用Unicode来表示非英语字符，我们还可以使用相同的位掩码技术将Unicode字符串转换为二进制字符串。

This example converts a single Chinese character 你 (It means you in English) to a binary string.

package com.mkyong.crypto.bytes;

import java.nio.charset.StandardCharsets;

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

public class UnicodeToBinary01 {

public static void main(String[] args) {

byte[] input = "你".getBytes(StandardCharsets.UTF_8);

System.out.println(input.length);// 3, 1 Chinese character = 3 bytes

String binary = convertByteArraysToBinary(input);

System.out.println(binary);

System.out.println(prettyBinary(binary, 8, " "));

}

public static String convertByteArraysToBinary(byte[] input) {

StringBuffer result = new StringBuffer();

for (byte b : input) {

int val = b;

for (int i = 0; i < 8; i++) {

result.append((val & 128) == 0 ? 0 : 1); // 128 = 1000 0000

val <<= 1;

}

}

return result.toString();

}

public static String prettyBinary(String binary, int blockSize, String separator) {

List result = new ArrayList<>();

int index = 0;

while (index < binary.length()) {

result.add(binary.substring(index, Math.min(index + blockSize, binary.length())));

index += blockSize;

}

return result.stream().collect(Collectors.joining(separator));

}

}

Output

3

111001001011110110100000

11100100 10111101 10100000

Different Unicode requires different bytes, and not all Chinese characters required 3 bytes of storage, some may need more or fewer bytes.

不同的Unicode需要不同的字节，并非所有汉字都需要3个字节的存储空间，有些可能需要更多或更少的字节。

5. Convert Binary to Unicode String.

Read comments for self-explanatory.

package com.mkyong.crypto.bytes;

import java.nio.ByteBuffer;

import java.nio.charset.StandardCharsets;

public class UnicodeToBinary02 {

public static void main(String[] args) {

String binary = "111001001011110110100000"; // 你, Chinese character

String result = binaryUnicodeToString(binary);

System.out.println(result.trim());

}

// <= 32bits = 4 bytes, int needs 4 bytes

public static String binaryUnicodeToString(String binary) {

byte[] array = ByteBuffer.allocate(4)

.putInt(Integer.parseInt(binary, 2)) // 4 bytes byte[]

.array();

return new String(array, StandardCharsets.UTF_8);

}

}

Output

你