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JAVA实现MD5算法、SHA1算法和SHA256算法

MD5、SHA1和SHA256是常见的哈希算法。JAVA中的hashCode是int类型，占64位。MD5生成128位哈希码，SHA1生成160位哈希码，SHA256生成256位哈希码。

MD5计算hashCode

以下是一个实现MD5算法的JAVA类：

package utils;import org.junit.Test;import java.security.MessageDigest;public class MD5Utils {    public static String md5Code(String input) {        try {            MessageDigest digest = MessageDigest.getInstance("MD5");            byte[] hash = digest.digest(input.getBytes("UTF-8"));            StringBuilder hexString = new StringBuilder();            for (int i = 0; i < hash.length; i++) {                String hex = Integer.toHexString(0xff & hash[i]);                if (hex.length() == 1) {                    hexString.append('0');                }                hexString.append(hex);            }            return hexString.toString();        } catch (Exception e) {            throw new RuntimeException(e);        }    }    @Test    public void test() {        String str = "Welcome";        String res = md5Code(str);        System.out.println(res);    }}

SHA1计算hashCode

以下是一个实现SHA1算法的JAVA类：

package utils;import org.junit.Test;import java.security.MessageDigest;public class SHA1Utils {    public static String sha1Code(String input) {        try {            MessageDigest digest = MessageDigest.getInstance("SHA1");            byte[] hash = digest.digest(input.getBytes("UTF-8"));            StringBuilder hexString = new StringBuilder();            for (int i = 0; i < hash.length; i++) {                String hex = Integer.toHexString(0xff & hash[i]);                if (hex.length() == 1) {                    hexString.append('0');                }                hexString.append(hex);            }            return hexString.toString();        } catch (Exception e) {            throw new RuntimeException(e);        }    }    @Test    public void test() {        String str = "Welcome";        String res = sha1Code(str);        System.out.println(res);    }}

SHA256计算hashCode

以下是一个实现SHA256算法的JAVA类：

package utils;import org.junit.Test;import java.security.MessageDigest;public class SHA256Utils {    public static String sha256Code(String input) {        try {            MessageDigest digest = MessageDigest.getInstance("SHA-256");            byte[] hash = digest.digest(input.getBytes("UTF-8"));            StringBuffer hexString = new StringBuffer();            for (int i = 0; i < hash.length; i++) {                String hex = Integer.toHexString(0xff & hash[i]);                if (hex.length() == 1) {                    hexString.append('0');                }                hexString.append(hex);            }            return hexString.toString();        } catch (Exception e) {            throw new RuntimeException(e);        }    }    @Test    public void test() {        String value = "Welcome";        String res = sha256Code(value);        System.out.println(res);    }}

以上代码均为JAVA实现MD5、SHA1和SHA256算法的示例代码，具体实现细节可根据实际需求进行调整。

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