Java 错误：线程中出现异常；“主要”；错误：未解决的编译问题
我正在观看一个面向初学者的Java教程，在编写代码时，我遇到了一些错误：Java 错误：线程中出现异常；“主要”；错误：未解决的编译问题,java,Java,我正在观看一个面向初学者的Java教程，在编写代码时，我遇到了一些错误： Exception in thread "main" java.lang.Error: Unresolved compilation problems: Syntax error, 'for each' statements are only available if source level is 1.5 or greater Arrays cannot be resolved Arrays c
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
Syntax error, 'for each' statements are only available if source level is 1.5 or greater
Arrays cannot be resolved
Arrays cannot be resolved
Arrays cannot be resolved
at Animal.main(Animal.java:389)
import java.util.Scanner;
// A class defines the attributes (fields) and capabilities (methods) of a real world object
public class Animal {
// static means this number is shared by all objects of type Animal
// final means that this value can't be changed
public static final double FAVNUMBER = 1.6180;
// Variables (Fields) start with a letter, underscore or $
// Private fields can only be accessed by other methods in the class
// Strings are objects that hold a series of characters
private String name;
// An integer can hold values from -2 ^ 31 to (2 ^ 31) -1
private int weight;
// Booleans have a value of true or false
private boolean hasOwner = false;
// Bytes can hold the values between -128 to 127
private byte age;
// Longs can hold the values between -2 ^ 63 to (2 ^ 63) - 1
private long uniqueID;
// Chars are unsigned ints that represent UTF-16 codes from 0 to 65,535
private char favoriteChar;
// Doubles are 64 bit IEEE 754 floating points with decimal values
private double speed;
// Floats are 32 bit IEEE 754 floating points with decimal values
private float height;
// Static variables have the same value for every object
// Any variable or function that doesn't make sense for an object to have should be made static
// protected means that this value can only be accessed by other code in the same package
// or by subclasses in other packages
protected static int numberOfAnimals = 0;
// A Scanner object allows you to except user input from the keyboard
static Scanner userInput = new Scanner(System.in);
// Any time an Animal object is created this function called the constructor is called
// to initialize the object
public Animal(){
// Shorthand for numberOfAnimals = numberOfAnimals + 1;
numberOfAnimals++;
int sumOfNumbers = 5 + 1;
System.out.println("5 + 1 = " + sumOfNumbers);
int diffOfNumbers = 5 - 1;
System.out.println("5 - 1 = " + diffOfNumbers);
int multOfNumbers = 5 * 1;
System.out.println("5 * 1 = " + multOfNumbers);
int divOfNumbers = 5 / 1;
System.out.println("5 / 1 = " + divOfNumbers);
int modOfNumbers = 5 % 3;
System.out.println("5 % 3 = " + modOfNumbers);
// print is used to print to the screen, but it doesn't end with a newline \n
System.out.print("Enter the name: \n");
// The if statement performs the actions between the { } if the condition is true
// userInput.hasNextLine() returns true if a String was entered in the keyboard
if(userInput.hasNextLine()){
// this provides you with a way to refer to the object itself
// userInput.nextLine() returns the value that was entered at the keyboard
this.setName(userInput.nextLine());
// hasNextInt, hasNextFloat, hasNextDouble, hasNextBoolean, hasNextByte,
// hasNextLong, nextInt, nextDouble, nextFloat, nextBoolean, etc.
}
this.setFavoriteChar();
this.setUniqueID();
}
// It is good to use getter and setter methods so that you can protect your data
// In Eclipse Right Click -> Source -> Generate Getter and Setters
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public boolean isHasOwner() {
return hasOwner;
}
public void setHasOwner(boolean hasOwner) {
this.hasOwner = hasOwner;
}
public byte getAge() {
return age;
}
public void setAge(byte age) {
this.age = age;
}
public long getUniqueID() {
return uniqueID;
}
// Method overloading allows you to accept different input with the same method name
public void setUniqueID(long uniqueID) {
this.uniqueID = uniqueID;
System.out.println("Unique ID set to: " + this.uniqueID);
}
public void setUniqueID() {
long minNumber = 1;
long maxNumber = 1000000;
// Generates a random number between 1 and 1000000
this.uniqueID = minNumber + (long)(Math.random() * ((maxNumber - minNumber) + 1));
// You can cast from one primitive value into another by putting what you want between ( )
// (byte) (short) (long) (double)
// (float), (boolean) & (char) don't work.
// (char) stays as a number instead of a character
// You convert from a primitive to a string like this
String stringNumber = Long.toString(maxNumber);
// Byte.toString(bigByte); Short.toString(bigShort); Integer.toString(bigInt);
// Float.toString(bigFloat); Double.toString(bigDouble); Boolean.toString(trueOrFalse);
// You convert from a String to a primitive like this
int numberString = Integer.parseInt(stringNumber);
// parseShort, parseLong, parseByte, parseFloat, parseDouble, parseBoolean
System.out.println("Unique ID set to: " + this.uniqueID);
}
public char getFavoriteChar() {
return favoriteChar;
}
public void setFavoriteChar(char favoriteChar) {
this.favoriteChar = favoriteChar;
}
public void setFavoriteChar() {
int randomNumber = (int) (Math.random() * 126) + 1;
this.favoriteChar = (char) randomNumber;
// if then else statement
// > < == != >= <=
if(randomNumber == 32){
System.out.println("Favorite character set to: Space");
} else if(randomNumber == 10){
System.out.println("Favorite character set to: New Line");
} else {
System.out.println("Favorite character set to: " + this.favoriteChar);
}
// Logical operators
// ! : Converts the boolean value to its right to its opposite form ie. true to false
// & : Returns true if boolean value on the right and left are both true (Always evaluates both boolean values)
// && : Returns true if boolean value on the right and left are both true (Stops evaluating after first false)
// | : Returns true if either boolean value on the right or left are true (Always evaluates both boolean values)
// || : Returns true if either boolean value on the right or left are true (Stops evaluating after first true)
// ^ : Returns true if there is 1 true and 1 false boolean value on the right or left
if((randomNumber > 97) && (randomNumber < 122)){
System.out.println("Favorite character is a lowercase letter");
}
if(((randomNumber > 97) && (randomNumber < 122)) || ((randomNumber > 64) && (randomNumber < 91))){
System.out.println("Favorite character is a letter");
}
if(!false){
System.out.println("I turned false to " + !false);
}
// The ternary operator assigns one or another value based on a condition
int whichIsBigger = (50 > randomNumber) ? 50 : randomNumber;
System.out.println("The biggest number is " + whichIsBigger);
// The switch statement is great for when you have a limited number of values
// and the values are int, byte, or char unless you have Java 7 which allows Strings
switch(randomNumber){
case 8 :
System.out.println("Favorite character set to: Backspace");
break;
case 9 :
System.out.println("Favorite character set to: Horizontal Tab");
break;
case 10 :
case 11 :
case 12 :
System.out.println("Favorite character set to: Something else weird");
break;
default :
System.out.println("Favorite character set to: " + this.favoriteChar);
break;
}
}
public double getSpeed() {
return speed;
}
public void setSpeed(double speed) {
this.speed = speed;
}
public float getHeight() {
return height;
}
public void setHeight(float height) {
this.height = height;
}
protected static int getNumberOfAnimals() {
return numberOfAnimals;
}
// Since numberOfAnimals is Static you must set the value using the class name
public void setNumberOfAnimals(int numberOfAnimals) {
Animal.numberOfAnimals = numberOfAnimals;
}
protected static void countTo(int startingNumber){
for(int i = startingNumber; i <= 100; i++){
// continue is used to skip 1 iteration of the loop
if(i == 90) continue;
System.out.println(i);
}
}
protected static String printNumbers(int maxNumbers){
int i = 1;
while(i < (maxNumbers / 2)){
System.out.println(i);
i++;
// This isn't needed, but if you want to jump out of a loop use break
if(i == (maxNumbers/2)) break;
}
Animal.countTo(maxNumbers/2);
// You can return a value like this
return "End of printNumbers()";
}
protected static void guessMyNumber(){
int number;
// Do while loops are used when you want to execute the code in the braces at least once
do {
System.out.println("Guess my number up to 100");
// If what they entered isn't a number send a warning
while(!userInput.hasNextInt()){
String numberEntered = userInput.next();
System.out.printf("%s is not a number\n", numberEntered);
}
number = userInput.nextInt();
}while(number != 50);
System.out.println("Yes the number was 50");
}
// This will be used to demonstrate polymorphism
public String makeSound(){
return "Grrrr";
}
// With polymorphism we can refer to any Animal and yet use overridden methods
// in the specific animal type
public static void speakAnimal(Animal randAnimal){
System.out.println("Animal says " + randAnimal.makeSound());
}
// public allows other classes to use this method
// static means that only a class can call for this to execute
// void means it doesn't return a value when it finishes executing
// This method can except Strings that can be stored in the String array args when it is executed
public static void main(String[] args){
Animal theDog = new Animal();
System.out.println("The animal is named " + theDog.getName());
System.out.println(Animal.printNumbers(100));
Animal.countTo(100);
Animal.guessMyNumber();
// An array is a fixed series of boxes that contain multiple values of the same data type
// How you create arrays
// int[] favoriteNumbers;
// favoriteNumbers = new int[20];
int[] favoriteNumbers = new int[20];
favoriteNumbers[0] = 100;
String[] stringArray = {"Random", "Words", "Here"};
// for(dataType[] varForRow : arrayName)
for(String word : stringArray)
{
System.out.println(word);
}
// This is a multidimensional array
String[][][] arrayName = { { { "000" }, { "100" }, { "200" }, { "300" } },
{ { "010" }, { "110" }, { "210" }, { "310" } },
{ { "020" }, { "120" }, { "220" }, { "320" } }};
for(int i = 0; i < arrayName.length; i++)
{
for(int j = 0; j < arrayName[i].length; j++)
{
for(int k = 0; k < arrayName[i][j].length; k++)
{
System.out.print("| " + arrayName[i][j][k] + " ");
}
}
System.out.println("|");
}
// You can copy an array (stringToCopy, indexes to copy)
String[] cloneOfArray = Arrays.copyOf(stringArray, 3);
// You can print out the whole array
System.out.println(Arrays.toString(cloneOfArray));
// Returns the index or a negative number
System.out.println(Arrays.binarySearch(cloneOfArray, "Random"));
}
}
public static void main(String[] args) {
Animal fido = new Dog();
Animal fluffy = new Cat();
// We can have an array of Animals that contain more specific subclasses
// Any overridden methods are used instead because of polymorphism
Animal[] theAnimals = new Animal[10];
theAnimals[0] = fido;
theAnimals[1] = fluffy;
System.out.println("Fido says " + theAnimals[0].makeSound());
System.out.println("Fluffy says " + theAnimals[1].makeSound());
// We can also pass subclasses of Animal and they just work
speakAnimal(fluffy);
}
}
谢谢 从错误消息中可以清楚地看到问题-
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
Syntax error, 'for each' statements are only available if source level is 1.5 or greater
或者你可以按照ultimate所说的去做，让你的循环与java的较低版本兼容（尽管我建议升级到1.5以上，但1.5与非常旧的版本很相似）。for（String word:stringArray）是一个所谓的“for each”循环，这是java 1.5中增加的一个便利 但编译器的配置似乎低于1.5，因此它不支持for-each循环 因此，您可以：
- 更改编译器级别
- 将循环更改为1.4兼容到
String[] stringArray = {"Random", "Words", "Here"}; String word; for(int i = 0; i < stringArray.length; i++) { word = stringArray[i]; System.out.println(word); }
（事实上，这就是编译器为您所做的…）String[]stringArray={“Random”，“Words”，“Here”}； 字符串字； 对于（int i=0；i
语法错误，“for each”语句仅在源代码级别为1.5或更高时可用echo%JAVA\u PATH%String[] stringArray = {"Random", "Words", "Here"};
String word;
for(int i = 0; i < stringArray.length; i++)
{
word = stringArray[i];
System.out.println(word);
}