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我正在尝试使用open-nlp Ruby gem通过RJB(Ruby Java Bridge)访问Java OpenNLP处理器。我不是Java程序员,所以我不知道该如何解决。关于解决,调试,收集更多信息等的任何建议将不胜感激。
环境是Windows 8,Ruby 1.9.3p448,Rails 4.0.0,JDK 1.7.0-40 x586。宝石是rjb 1.4.8和louismullie / open-nlp 0.1.4。作为记录,该文件在JRuby中运行,但是在该环境中我遇到了其他问题,因此暂时保留本机Ruby。
简而言之,open-nlp gem失败,缺少java.lang.NullPointerException和Ruby错误方法。我犹豫要说为什么会这样,因为我不知道,但是在我看来,无法访问Jars文件opennlp.tools.postag.POSTaggerME@1b5080a的动态加载,可能是因为OpenNLP::Bindings::Utils .tagWithArrayList设置不正确。 OpenNLP::Bindings是Ruby。实用程序及其方法是Java。 Utils应该是“默认”的Jars和Class文件,这可能很重要。
我在做什么错,在这里?谢谢!
我正在运行的代码直接从github/open-nlp复制而来。我的代码副本是:
class OpennlpTryer
$DEBUG=false
# From https://github.com/louismullie/open-nlp
# Hints: Dir.pwd; File.expand_path('../../Gemfile', __FILE__);
# Load the module
require 'open-nlp'
#require 'jruby-jars'
=begin
# Alias "write" to "print" to monkeypatch the NoMethod write error
java_import java.io.PrintStream
class PrintStream
java_alias(:write, :print, [java.lang.String])
end
=end
=begin
# Display path of jruby-jars jars...
puts JRubyJars.core_jar_path # => path to jruby-core-VERSION.jar
puts JRubyJars.stdlib_jar_path # => path to jruby-stdlib-VERSION.jar
=end
puts ENV['CLASSPATH']
# Set an alternative path to look for the JAR files.
# Default is gem's bin folder.
# OpenNLP.jar_path = '/path_to_jars/'
OpenNLP.jar_path = File.join(ENV["GEM_HOME"],"gems/open-nlp-0.1.4/bin/")
puts OpenNLP.jar_path
# Set an alternative path to look for the model files.
# Default is gem's bin folder.
# OpenNLP.model_path = '/path_to_models/'
OpenNLP.model_path = File.join(ENV["GEM_HOME"],"gems/open-nlp-0.1.4/bin/")
puts OpenNLP.model_path
# Pass some alternative arguments to the Java VM.
# Default is ['-Xms512M', '-Xmx1024M'].
# OpenNLP.jvm_args = ['-option1', '-option2']
OpenNLP.jvm_args = ['-Xms512M', '-Xmx1024M']
# Redirect VM output to log.txt
OpenNLP.log_file = 'log.txt'
# Set default models for a language.
# OpenNLP.use :language
OpenNLP.use :english # Make sure this is lower case!!!!
# Simple tokenizer
OpenNLP.load
sent = "The death of the poet was kept from his poems."
tokenizer = OpenNLP::SimpleTokenizer.new
tokens = tokenizer.tokenize(sent).to_a
# => %w[The death of the poet was kept from his poems .]
puts "Tokenize #{tokens}"
# Maximum entropy tokenizer, chunker and POS tagger
OpenNLP.load
chunker = OpenNLP::ChunkerME.new
tokenizer = OpenNLP::TokenizerME.new
tagger = OpenNLP::POSTaggerME.new
sent = "The death of the poet was kept from his poems."
tokens = tokenizer.tokenize(sent).to_a
# => %w[The death of the poet was kept from his poems .]
puts "Tokenize #{tokens}"
tags = tagger.tag(tokens).to_a
# => %w[DT NN IN DT NN VBD VBN IN PRP$ NNS .]
puts "Tags #{tags}"
chunks = chunker.chunk(tokens, tags).to_a
# => %w[B-NP I-NP B-PP B-NP I-NP B-VP I-VP B-PP B-NP I-NP O]
puts "Chunks #{chunks}"
# Abstract Bottom-Up Parser
OpenNLP.load
sent = "The death of the poet was kept from his poems."
parser = OpenNLP::Parser.new
parse = parser.parse(sent)
=begin
parse.get_text.should eql sent
parse.get_span.get_start.should eql 0
parse.get_span.get_end.should eql 46
parse.get_child_count.should eql 1
=end
child = parse.get_children[0]
child.text # => "The death of the poet was kept from his poems."
child.get_child_count # => 3
child.get_head_index #=> 5
child.get_type # => "S"
puts "Child: #{child}"
# Maximum Entropy Name Finder*
OpenNLP.load
# puts File.expand_path('.', __FILE__)
text = File.read('./spec/sample.txt').gsub!("\n", "")
tokenizer = OpenNLP::TokenizerME.new
segmenter = OpenNLP::SentenceDetectorME.new
puts "Tokenizer: #{tokenizer}"
puts "Segmenter: #{segmenter}"
ner_models = ['person', 'time', 'money']
ner_finders = ner_models.map do |model|
OpenNLP::NameFinderME.new("en-ner-#{model}.bin")
end
puts "NER Finders: #{ner_finders}"
sentences = segmenter.sent_detect(text)
puts "Sentences: #{sentences}"
named_entities = []
sentences.each do |sentence|
tokens = tokenizer.tokenize(sentence)
ner_models.each_with_index do |model, i|
finder = ner_finders[i]
name_spans = finder.find(tokens)
name_spans.each do |name_span|
start = name_span.get_start
stop = name_span.get_end-1
slice = tokens[start..stop].to_a
named_entities << [slice, model]
end
end
end
puts "Named Entities: #{named_entities}"
# Loading specific models
# Just pass the name of the model file to the constructor. The gem will search for the file in the OpenNLP.model_path folder.
OpenNLP.load
tokenizer = OpenNLP::TokenizerME.new('en-token.bin')
tagger = OpenNLP::POSTaggerME.new('en-pos-perceptron.bin')
name_finder = OpenNLP::NameFinderME.new('en-ner-person.bin')
# etc.
puts "Tokenizer: #{tokenizer}"
puts "Tagger: #{tagger}"
puts "Name Finder: #{name_finder}"
# Loading specific classes
# You may want to load specific classes from the OpenNLP library that are not loaded by default. The gem provides an API to do this:
# Default base class is opennlp.tools.
OpenNLP.load_class('SomeClassName')
# => OpenNLP::SomeClassName
# Here, we specify another base class.
OpenNLP.load_class('SomeOtherClass', 'opennlp.tools.namefind')
# => OpenNLP::SomeOtherClass
end
tags = tagger.tag(tokens).to_a #
# => %w[DT NN IN DT NN VBD VBN IN PRP$ NNS .]
class OpenNLP::POSTaggerME < OpenNLP::Base
unless RUBY_PLATFORM =~ /java/
def tag(*args)
OpenNLP::Bindings::Utils.tagWithArrayList(@proxy_inst, args[0]) # <== Line 13
end
end
end
# Add in Rjb workarounds.
unless RUBY_PLATFORM =~ /java/
self.default_jars << 'utils.jar'
self.default_classes << ['Utils', '']
end
.;C:\Program Files (x86)Java\jdk1.7.0_40\lib;C:\Program Files (x86)Java\jre7\lib;D:\BitNami\rubystack-1.9.3-12\ruby\lib\ruby\gems\1.9.1\gems\open-nlp-0.1.4\bin
jwnl-1.3.3.jar
opennlp-maxent-3.0.2-incubating.jar
opennlp-tools-1.5.2-incubating.jar
opennlp-uima-1.5.2-incubating.jar
utils.jar
Utils.java
import java.util.Arrays;
import java.util.ArrayList;
import java.lang.String;
import opennlp.tools.postag.POSTagger;
import opennlp.tools.chunker.ChunkerME;
import opennlp.tools.namefind.NameFinderME; // interface instead?
import opennlp.tools.util.Span;
// javac -cp '.:opennlp.tools.jar' Utils.java
// jar cf utils.jar Utils.class
public class Utils {
public static String[] tagWithArrayList(POSTagger posTagger, ArrayList[] objectArray) {
return posTagger.tag(getStringArray(objectArray));
}
public static Object[] findWithArrayList(NameFinderME nameFinder, ArrayList[] tokens) {
return nameFinder.find(getStringArray(tokens));
}
public static Object[] chunkWithArrays(ChunkerME chunker, ArrayList[] tokens, ArrayList[] tags) {
return chunker.chunk(getStringArray(tokens), getStringArray(tags));
}
public static String[] getStringArray(ArrayList[] objectArray) {
String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);
return stringArray;
}
}
D:\BitNami\rubystack-1.9.3-12\ruby\bin\ruby.exe -e $stdout.sync=true;$stderr.sync=true;load($0=ARGV.shift) D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb
.;C:\Program Files (x86)\Java\jdk1.7.0_40\lib;C:\Program Files (x86)\Java\jre7\lib;D:\BitNami\rubystack-1.9.3-12\ruby\lib\ruby\gems\1.9.1\gems\open-nlp-0.1.4\bin
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/bin/
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/bin/
Tokenize ["The", "death", "of", "the", "poet", "was", "kept", "from", "his", "poems", "."]
Tokenize ["The", "death", "of", "the", "poet", "was", "kept", "from", "his", "poems", "."]
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:13:in `method_missing': unknown exception (NullPointerException)
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:13:in `tag'
from D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:73:in `<class:OpennlpTryer>'
from D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'
import java.util.Arrays;
import java.util.Object;
import java.lang.String;
import opennlp.tools.postag.POSTagger;
import opennlp.tools.chunker.ChunkerME;
import opennlp.tools.namefind.NameFinderME; // interface instead?
import opennlp.tools.util.Span;
// javac -cp '.:opennlp.tools.jar' Utils.java
// jar cf utils.jar Utils.class
public class Utils {
public static String[] tagWithArrayList(POSTagger posTagger, Object[] objectArray) {
return posTagger.tag(getStringArray(objectArray));
}f
public static Object[] findWithArrayList(NameFinderME nameFinder, Object[] tokens) {
return nameFinder.find(getStringArray(tokens));
}
public static Object[] chunkWithArrays(ChunkerME chunker, Object[] tokens, Object[] tags) {
return chunker.chunk(getStringArray(tokens), getStringArray(tags));
}
public static String[] getStringArray(Object[] objectArray) {
String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);
return stringArray;
}
}
Uncaught exception: uninitialized constant OpennlpTryer::ArrayStoreException
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:81:in `rescue in <class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:77:in `<class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
Uncaught exception: uninitialized constant OpennlpTryer::ArrayStoreException
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:81:in `rescue in <class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:77:in `<class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
Uncaught exception: uninitialized constant OpenNLP::POSTaggerME::ArrayStoreException
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:16:in `rescue in tag'
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:13:in `tag'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:78:in `<class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
Uncaught exception: unknown exception
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:15:in `method_missing'
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp/classes.rb:15:in `tag'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:78:in `<class:OpennlpTryer>'
D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
import java.util.Arrays;
import java.util.ArrayList;
import java.lang.String;
import opennlp.tools.postag.POSTagger;
import opennlp.tools.chunker.ChunkerME;
import opennlp.tools.namefind.NameFinderME; // interface instead?
import opennlp.tools.util.Span;
// javac -cp '.:opennlp.tools.jar' Utils.java
// jar cf utils.jar Utils.class
public class Utils {
public static String[] tagWithArrayList(
System.out.println("Tokens: ("+objectArray.getClass().getSimpleName()+"): \n"+objectArray);
POSTagger posTagger, ArrayList[] objectArray) {
return posTagger.tag(getStringArray(objectArray));
}
public static Object[] findWithArrayList(NameFinderME nameFinder, ArrayList[] tokens) {
return nameFinder.find(getStringArray(tokens));
}
public static Object[] chunkWithArrays(ChunkerME chunker, ArrayList[] tokens, ArrayList[] tags) {
return chunker.chunk(getStringArray(tokens), getStringArray(tags));
}
public static String[] getStringArray(ArrayList[] objectArray) {
String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);
return stringArray;
}
}
import java.util.ArrayList;
import java.util.Arrays;
import opennlp.tools.chunker.ChunkerME;
import opennlp.tools.namefind.NameFinderME;
import opennlp.tools.postag.POSTagger;
public class Utils
{
public Utils()
{
}
public static String[] tagWithArrayList(POSTagger postagger, ArrayList aarraylist[])
{
return postagger.tag(getStringArray(aarraylist));
}
public static Object[] findWithArrayList(NameFinderME namefinderme, ArrayList aarraylist[])
{
return namefinderme.find(getStringArray(aarraylist));
}
public static Object[] chunkWithArrays(ChunkerME chunkerme, ArrayList aarraylist[], ArrayList aarraylist1[])
{
return chunkerme.chunk(getStringArray(aarraylist), getStringArray(aarraylist1));
}
public static String[] getStringArray(ArrayList aarraylist[])
{
String as[] = (String[])Arrays.copyOf(aarraylist, aarraylist.length, [Ljava/lang/String;);
return as;
}
}
import java.util.Arrays;
import java.util.ArrayList;
import java.lang.String;
import opennlp.tools.postag.POSTagger;
import opennlp.tools.chunker.ChunkerME;
import opennlp.tools.namefind.NameFinderME; // interface instead?
import opennlp.tools.util.Span;
// javac -cp '.:opennlp.tools.jar' Utils.java
// jar cf utils.jar Utils.class
public class Utils {
public static String[] tagWithArrayList(POSTagger posTagger, ArrayList[] objectArray) {
return posTagger.tag(getStringArray(objectArray));
}
public static Object[] findWithArrayList(NameFinderME nameFinder, ArrayList[] tokens) {
return nameFinder.find(getStringArray(tokens));
}
public static Object[] chunkWithArrays(ChunkerME chunker, ArrayList[] tokens, ArrayList[] tags) {
return chunker.chunk(getStringArray(tokens), getStringArray(tags));
}
public static String[] getStringArray(ArrayList[] objectArray) {
String[] stringArray = Arrays.copyOf(objectArray, objectArray.length, String[].class);
return stringArray;
}
}
# Private function to load classes.
# Doesn't check if initialized.
def load_klass(klass, base, name=nil)
base += '.' unless base == ''
fqcn = "#{base}#{klass}"
name ||= klass
if RUBY_PLATFORM =~ /java/
rb_class = java_import(fqcn)
if name != klass
if rb_class.is_a?(Array)
rb_class = rb_class.first
end
const_set(name.intern, rb_class)
end
else
rb_class = Rjb::import(fqcn) # <== This is line 110
const_set(name.intern, rb_class)
end
end
D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:110:in `import': opennlp/tools/namefind/NameFinderME (NoClassDefFoundError)
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:110:in `load_klass'
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:89:in `block in load_default_classes'
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:87:in `each'
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:87:in `load_default_classes'
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/bind-it-0.2.7/lib/bind-it/binding.rb:56:in `bind'
from D:/BitNami/rubystack-1.9.3-12/ruby/lib/ruby/gems/1.9.1/gems/open-nlp-0.1.4/lib/open-nlp.rb:14:in `load'
from D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:54:in `<class:OpennlpTryer>'
from D:/BitNami/rubystack-1.9.3-12/projects/RjbTest/app/helpers/opennlp_tryer.rb:1:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'
OpenNLP.load
# Default JARs to load.
self.default_jars = [
'jwnl-1.3.3.jar',
'opennlp-tools-1.5.2-incubating.jar',
'opennlp-maxent-3.0.2-incubating.jar',
'opennlp-uima-1.5.2-incubating.jar'
]
# Default namespace.
self.default_namespace = 'opennlp.tools'
# Default classes.
self.default_classes = [
# OpenNLP classes.
['AbstractBottomUpParser', 'opennlp.tools.parser'],
['DocumentCategorizerME', 'opennlp.tools.doccat'],
['ChunkerME', 'opennlp.tools.chunker'],
['DictionaryDetokenizer', 'opennlp.tools.tokenize'],
['NameFinderME', 'opennlp.tools.namefind'],
['Parser', 'opennlp.tools.parser.chunking'],
['Parse', 'opennlp.tools.parser'],
['ParserFactory', 'opennlp.tools.parser'],
['POSTaggerME', 'opennlp.tools.postag'],
['SentenceDetectorME', 'opennlp.tools.sentdetect'],
['SimpleTokenizer', 'opennlp.tools.tokenize'],
['Span', 'opennlp.tools.util'],
['TokenizerME', 'opennlp.tools.tokenize'],
# Generic Java classes.
['FileInputStream', 'java.io'],
['String', 'java.lang'],
['ArrayList', 'java.util']
]
# Add in Rjb workarounds.
unless RUBY_PLATFORM =~ /java/
self.default_jars << 'utils.jar'
self.default_classes << ['Utils', '']
end
最佳答案
在完整的CLASSES.RB模块末尾查看完整代码
我今天遇到了同样的问题。我不太了解为什么要使用Utils类,因此我以以下方式修改了classes.rb文件:
unless RUBY_PLATFORM =~ /java/
def tag(*args)
@proxy_inst.tag(args[0])
#OpenNLP::Bindings::Utils.tagWithArrayList(@proxy_inst, args[0])
end
end
sent = "The death of the poet was kept from his poems."
tokens = tokenizer.tokenize(sent).to_a
# => %w[The death of the poet was kept from his poems .]
tags = tagger.tag(tokens).to_a
# => ["prop", "prp", "n", "v-fin", "n", "adj", "prop", "v-fin", "n", "adj", "punc"]
def chunk(tokens, tags)
chunks = @proxy_inst.chunk(tokens, tags)
# chunks = OpenNLP::Bindings::Utils.chunkWithArrays(@proxy_inst, tokens,tags)
chunks.map { |c| c.to_s }
end
class OpenNLP::NameFinderME < OpenNLP::Base
unless RUBY_PLATFORM =~ /java/
def find(*args)
@proxy_inst.find(args[0])
# OpenNLP::Bindings::Utils.findWithArrayList(@proxy_inst, args[0])
end
end
end
require 'open-nlp/base'
class OpenNLP::SentenceDetectorME < OpenNLP::Base; end
class OpenNLP::SimpleTokenizer < OpenNLP::Base; end
class OpenNLP::TokenizerME < OpenNLP::Base; end
class OpenNLP::POSTaggerME < OpenNLP::Base
unless RUBY_PLATFORM =~ /java/
def tag(*args)
@proxy_inst._invoke("tag", "[Ljava.lang.String;", args[0])
end
end
end
class OpenNLP::ChunkerME < OpenNLP::Base
if RUBY_PLATFORM =~ /java/
def chunk(tokens, tags)
if !tokens.is_a?(Array)
tokens = tokens.to_a
tags = tags.to_a
end
tokens = tokens.to_java(:String)
tags = tags.to_java(:String)
@proxy_inst.chunk(tokens,tags).to_a
end
else
def chunk(tokens, tags)
chunks = @proxy_inst._invoke("chunk", "[Ljava.lang.String;[Ljava.lang.String;", tokens, tags)
chunks.map { |c| c.to_s }
end
end
end
class OpenNLP::Parser < OpenNLP::Base
def parse(text)
tokenizer = OpenNLP::TokenizerME.new
full_span = OpenNLP::Bindings::Span.new(0, text.size)
parse_obj = OpenNLP::Bindings::Parse.new(
text, full_span, "INC", 1, 0)
tokens = tokenizer.tokenize_pos(text)
tokens.each_with_index do |tok,i|
start, stop = tok.get_start, tok.get_end
token = text[start..stop-1]
span = OpenNLP::Bindings::Span.new(start, stop)
parse = OpenNLP::Bindings::Parse.new(text, span, "TK", 0, i)
parse_obj.insert(parse)
end
@proxy_inst.parse(parse_obj)
end
end
class OpenNLP::NameFinderME < OpenNLP::Base
unless RUBY_PLATFORM =~ /java/
def find(*args)
@proxy_inst._invoke("find", "[Ljava.lang.String;", args[0])
end
end
end
关于java - 使用RJB(Ruby Java Bridge)的OpenNLP中的java.lang.NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19018014/
我正在编写一个具有以下签名的 Java 方法。 void Logger(Method method, Object[] args); 如果一个方法(例如 ABC() )调用此方法 Logger,它应该
我是 Java 新手。 我的问题是我的 Java 程序找不到我试图用作的图像文件一个 JButton。 (目前这段代码什么也没做,因为我只是得到了想要的外观第一的)。这是我的主课 代码: packag
好的,今天我在接受采访,我已经编写 Java 代码多年了。采访中说“Java 垃圾收集是一个棘手的问题,我有几个 friend 一直在努力弄清楚。你在这方面做得怎么样?”。她是想骗我吗?还是我的一生都
我的 friend 给了我一个谜语让我解开。它是这样的: There are 100 people. Each one of them, in his turn, does the following
如果我将使用 Java 5 代码的应用程序编译成字节码,生成的 .class 文件是否能够在 Java 1.4 下运行? 如果后者可以工作并且我正在尝试在我的 Java 1.4 应用程序中使用 Jav
有关于why Java doesn't support unsigned types的问题以及一些关于处理无符号类型的问题。我做了一些搜索,似乎 Scala 也不支持无符号数据类型。限制是Java和S
我只是想知道在一个 java 版本中生成的字节码是否可以在其他 java 版本上运行 最佳答案 通常,字节码无需修改即可在 较新 版本的 Java 上运行。它不会在旧版本上运行,除非您使用特殊参数 (
我有一个关于在命令提示符下执行 java 程序的基本问题。 在某些机器上我们需要指定 -cp 。 (类路径)同时执行java程序 (test为java文件名与.class文件存在于同一目录下) jav
我已经阅读 StackOverflow 有一段时间了,现在我才鼓起勇气提出问题。我今年 20 岁,目前在我的家乡(罗马尼亚克卢日-纳波卡)就读 IT 大学。足以介绍:D。 基本上,我有一家提供簿记应用
我有 public JSONObject parseXML(String xml) { JSONObject jsonObject = XML.toJSONObject(xml); r
我已经在 Java 中实现了带有动态类型的简单解释语言。不幸的是我遇到了以下问题。测试时如下代码: def main() { def ks = Map[[1, 2]].keySet()
一直提示输入 1 到 10 的数字 - 结果应将 st、rd、th 和 nd 添加到数字中。编写一个程序,提示用户输入 1 到 10 之间的任意整数,然后以序数形式显示该整数并附加后缀。 public
我有这个 DownloadFile.java 并按预期下载该文件: import java.io.*; import java.net.URL; public class DownloadFile {
我想在 GUI 上添加延迟。我放置了 2 个 for 循环,然后重新绘制了一个标签,但这 2 个 for 循环一个接一个地执行,并且标签被重新绘制到最后一个。 我能做什么? for(int i=0;
我正在对对象 Student 的列表项进行一些测试,但是我更喜欢在 java 类对象中创建硬编码列表,然后从那里提取数据,而不是连接到数据库并在结果集中选择记录。然而,自从我这样做以来已经很长时间了,
我知道对象创建分为三个部分: 声明 实例化 初始化 classA{} classB extends classA{} classA obj = new classB(1,1); 实例化 它必须使用
我有兴趣使用 GPRS 构建车辆跟踪系统。但是,我有一些问题要问以前做过此操作的人: GPRS 是最好的技术吗?人们意识到任何问题吗? 我计划使用 Java/Java EE - 有更好的技术吗? 如果
我可以通过递归方法反转数组,例如:数组={1,2,3,4,5} 数组结果={5,4,3,2,1}但我的结果是相同的数组,我不知道为什么,请帮助我。 public class Recursion { p
有这样的标准方式吗? 包括 Java源代码-测试代码- Ant 或 Maven联合单元持续集成(可能是巡航控制)ClearCase 版本控制工具部署到应用服务器 最后我希望有一个自动构建和集成环境。
我什至不知道这是否可能,我非常怀疑它是否可能,但如果可以,您能告诉我怎么做吗?我只是想知道如何从打印机打印一些文本。 有什么想法吗? 最佳答案 这里有更简单的事情。 import javax.swin
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