大佬教程收集整理的这篇文章主要介绍了当我试图编译Java代码时，为什么会得到“Exception；must be catched or declared to be throw”？，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。
你所有的问题都源于此
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
@H_197_6@包含在try，catch块中的问题是，如果程序发现异常，则不返回任何内容。这样写（按照程序逻辑进行修改）：
public static byte[] encrypt(String toEncrypt) throws Exception{
try{
String plaintext = toEncrypt;
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(), "AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.geTinstance("AES/CBC/Nopadding");
cipher.init(Cipher.ENCRYPT_MODE,keyspec,ivspec);
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
} catch(Exception E){
return null; // Always must return something
}
}
@H_197_6@对于第二个，你必须从crypto@H_197_6@方法调用中捕获Exception@H_197_6@ ，如下所示（也可以在程序逻辑上对其进行修改）：
public voID actionPerformed(ActionEvent E)
.
.
.
try {
byte[] encrypted = encrypt(concatURL);
String encryptedString = bytesToHex(encrypted);
content.removeAll();
content.add(new JLabel("Concatenated User input -->" + concatURL));
content.add(encryptedTextFIEld);
setContentPane(content);
} catch (Exception exC) {
// Todo: handle exception
}
}
@H_197_6@你必须从中吸取教训：
具有返回类型的方法必须始终返回该类型的对象，我的意思是在所有可能的情况下 必须始终处理所有检查的异常
考虑：
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
import java.io.*;
public class EncryptURL extends JApplet implements ActionListener {
Container content;
JTextField userName = new JTextField();
JTextField firstName = new JTextField();
JTextField lastName = new JTextField();
JTextField email = new JTextField();
JTextField phone = new JTextField();
JTextField heartbeatID = new JTextField();
JTextField regionCode = new JTextField();
JTextField retRegionCode = new JTextField();
JTextField encryptedTextField = new JTextField();
JPanel finishPanel = new JPanel();
public void init() {
//settitle("Book - E Project");
setSize(800,600);
content = getContentPane();
content.setBACkground(Color.yellow);
content.setLayout(new BoxLayout(content,BoxLayout.Y_AXIS));
JButton submit = new JButton("Submit");
content.add(new JLabel("User Name"));
content.add(userName);
content.add(new JLabel("First Name"));
content.add(firstName);
content.add(new JLabel("last name"));
content.add(lastName);
content.add(new JLabel("Email"));
content.add(email);
content.add(new JLabel("Phone"));
content.add(phonE);
content.add(new JLabel("HeartBeatID"));
content.add(heartbeatID);
content.add(new JLabel("Region Code"));
content.add(regionCodE);
content.add(new JLabel("RetRegionCode"));
content.add(retRegionCodE);
content.add(submit);
submit.addActionListener(this);
}
public void actionPerformed(ActionEvent E) {
if (e.getActionCommand() == "Submit"){
String subUserName = userName.getText();
String subFName = firstName.getText();
String subLName = lastName.getText();
String subEmail = email.getText();
String subPhone = phone.getText();
String subHeartbeatID = heartbeatID.getText();
String subRegionCode = regionCode.getText();
String subRetRegionCode = retRegionCode.getText();
String concatURL =
"user=" + subUserName + "&f=" + subFName +
"&l=" + subLName + "&em=" + subEmail +
"&p=" + subPhone + "&h=" + subHeartbeatID +
"&re=" + subRegionCode + "&ret=" + subRetRegionCode;
concatURL = padString(concatURL,' ',16);
byte[] encrypted = encrypt(concatURL);
String encryptedString = bytesToHex(encrypted);
content.removeAll();
content.add(new JLabel("Concatenated User Input -->" + concatURL));
content.add(encryptedTextField);
setContentPane(content);
}
}
public static byte[] encrypt(String toEncrypt) throws Exception{
try{
String plaintext = toEncrypt;
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(),"AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.geTinstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE,keyspec,ivspec);
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
}
catch(Exception E){
}
}
public static byte[] decrypt(byte[] toDecrypt) throws Exception{
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(),"AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.geTinstance("AES/CBC/NoPadding");
cipher.init(Cipher.DECRYPT_MODE,ivspec);
byte[] decrypted = cipher.doFinal(toDecrypt);
return decrypted;
}
public static String bytesToHex(byte[] data) {
if (data == null)
{
return null;
}
else
{
int len = data.length;
String str = "";
for (int i=0; i<len; i++)
{
if ((data[i]&0xFF) < 16)
str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
else
str = str + java.lang.Integer.toHexString(data[i]&0xFF);
}
return str;
}
}
public static String padString(String source,char paddingChar,int sizE)
{
int padLength = size-source.length() % size;
for (int i = 0; i < padLength; i++) {
source += paddingChar;
}
return source;
}
}
@H_197_6@我收到了一个未报告的异常：
java.lang.Exception; must be caught or declared to be thrown
byte[] encrypted = encrypt(concatURL);
@H_197_6@以及：
.java:109: missing return statement
@H_197_6@我该如何解决这些问题？
以上是大佬教程为你收集整理的当我试图编译Java代码时，为什么会得到“Exception；must be catched or declared to be throw”？全部内容，希望文章能够帮你解决当我试图编译Java代码时，为什么会得到“Exception；must be catched or declared to be throw”？所遇到的程序开发问题。
如果觉得大佬教程网站内容还不错，欢迎将大佬教程推荐给程序员好友。
本图文内容来源于网友网络收集整理提供，作为学习参考使用，版权属于原作者。
如您有任何意见或建议可联系处理。小编QQ：384754419，请注明来意。