java中list的使用方法

发布网友发布时间：2022-04-27 00:01

共2个回答

热心网友时间：2022-06-20 19:26

LIST是个容器接口，可以理解为动态数组，传统数组必须定义好数组的个数才可以使用，而容器对象无须定义好数组下标总数，用add()方法即可添加新的成员对象，他可以添加的仅仅只能为对象，不能添加基本数据类型，容器还对应get(),remove()方法来获取和删除数据成员

热心网友时间：2022-06-20 19:26

import java.io.*;
import java.awt.*; // AWT classes for the demo program
import javax.swing.*; // Swing GUI classes for the demo

/**
* This class contains a useful static method for listing all threads
* and threadgroups in the VM. It also has a simple main() method so it
* can be run as a standalone program.
**/
public class ThreadLister {
/** Display information about a thread. */
private static void printThreadInfo(PrintWriter out, Thread t,
String indent) {
if (t == null) return;
out.println(indent + "Thread: " + t.getName() +
" Priority: " + t.getPriority() +
(t.isDaemon()?" Daemon":"") +
(t.isAlive()?"":" Not Alive"));
}

/** Display info about a thread group and its threads and groups */
private static void printGroupInfo(PrintWriter out, ThreadGroup g,
String indent) {
if (g == null) return;
int num_threads = g.activeCount();
int num_groups = g.activeGroupCount();
Thread[] threads = new Thread[num_threads];
ThreadGroup[] groups = new ThreadGroup[num_groups];

g.enumerate(threads, false);
g.enumerate(groups, false);

out.println(indent + "Thread Group: " + g.getName() +
" Max Priority: " + g.getMaxPriority() +
(g.isDaemon()?" Daemon":""));

for(int i = 0; i < num_threads; i++)
printThreadInfo(out, threads[i], indent + " ");
for(int i = 0; i < num_groups; i++)
printGroupInfo(out, groups[i], indent + " ");
}

/** Find the root thread group and list it recursively */
public static void listAllThreads(PrintWriter out) {
ThreadGroup current_thread_group;
ThreadGroup root_thread_group;
ThreadGroup parent;

// Get the current thread group
current_thread_group = Thread.currentThread().getThreadGroup();

// Now go find the root thread group
root_thread_group = current_thread_group;
parent = root_thread_group.getParent();
while(parent != null) {
root_thread_group = parent;
parent = parent.getParent();
}

// And list it, recursively
printGroupInfo(out, root_thread_group, "");
}

/**
* The main() method create a simple graphical user interface to display
* the threads in. This allows us to see the "event dispatch thread" used
* by AWT and Swing.
**/
public static void main(String[] args) {
// Create a simple Swing GUI
JFrame frame = new JFrame("ThreadLister Demo");
JTextArea textarea = new JTextArea();
frame.getContentPane().add(new JScrollPane(textarea),
BorderLayout.CENTER);
frame.setSize(500, 400);
frame.setVisible(true);

// Get the threadlisting as a string using a StringWriter stream
StringWriter sout = new StringWriter(); // To capture the listing
PrintWriter out = new PrintWriter(sout);
ThreadLister.listAllThreads(out); // List threads to stream
out.close();
String threadListing = sout.toString(); // Get listing as a string

// Finally, display the thread listing in the GUI
textarea.setText(threadListing);
}
}