java当中的线程和操作系统的线程是什么关系？

 int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

#include <pthread.h>//头文件
#include <stdio.h>
pthread_t pid;//定义一个变量，接受创建线程后的线程id
//定义线程的主体函数
void* thread_entity(void* arg)
{   
    printf("i am new Thread!");
}
//main方法，程序入口，main和java的main一样会产生一个进程，继而产生一个main线程
int main()
{
    //调用操作系统的函数创建线程，注意四个参数
    pthread_create(&pid,NULL,thread_entity,NULL);
    //usleep是睡眠的意思，那么这里的睡眠是让谁睡眠呢？
    //为什么需要睡眠？如果不睡眠会出现什么情况
    usleep(100);
    printf("mainn");
}

public class Example4Start {

    public static void main(String[] args) {
        Thread thread = new Thread(){
            @Override
            public void run() {
                System.out.println("i am new Thread!");
            }
        }; 
        thread.start();
    }
}

public class LubanThread {
    public static void main(String[] args) {
        LubanThread lubanThread =new LubanThread();
        lubanThread.start0();
    }
    private native void start0();
}

#include <pthread.h>
#include <stdio.h>
pthread_t pid;
void* thread_entity(void* arg)
{   
    while(1){
        usleep(100);
        printf("I am new Threadn");
    }
}
int main()
{
    pthread_create(&pid,NULL,thread_entity,NULL);
    while(1){
        usleep(100);
        printf("I am  mainn");
    }
}

gcc thread.c -o thread.out -pthread
./thread.out 

package com.luban.concurrency;

public class LubanThread {
    static {
        System.loadLibrary( "LubanThreadNative" );
    }
    public static void main(String[] args) {
        LubanThread lubanThread =new LubanThread();
        lubanThread.start0();
    }
    private native void start0();
}

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_luban_concurrency_LubanThread */

#ifndef _Included_com_luban_concurrency_LubanThread
#define _Included_com_luban_concurrency_LubanThread
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_luban_concurrency_LubanThread
 * Method:    start0
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_luban_concurrency_LubanThread_start0
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

#include <pthread.h>
#include <stdio.h>
#include "com_luban_concurrency_LubanThread.h"//记得导入刚刚编译的那个.h文件
pthread_t pid;
void* thread_entity(void* arg)
{   
    while(1){
        usleep(100);
        printf("I am new Threadn");
    }
}

//这个方法要参考.h文件的15行代码，这里的参数得注意，你写死就行，不用明白为什么
JNIEXPORT void JNICALL Java_com_luban_concurrency_LubanThread_start0
(JNIEnv *env, jobject c1){
    pthread_create(&pid,NULL,thread_entity,NULL);
    while(1){
        usleep(100);
        printf("I am  mainn");
    }   
}

int main()
{
    return 0;
}

gcc  -fPIC -I /usr/lib/jvm/java-1.8.0-openjdk/include -I /usr/lib/jvm/java-1.8.0-openjdk/include/linux  -shared -o libLubanThreadNative.so threadNew.c

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:{libLubanThreadNative.so}所在的路径

package com.luban.concurrency;

public class LubanThread {
    static {
        System.loadLibrary( "LubanThreadNative" );
    }
    public static void main(String[] args) {
        LubanThread lubanThread =new LubanThread();
        lubanThread.start0();
    }
    //这个run方法，要让C程序员调用到，就完美了
    public void run(){
        System.out.println("I am java Thread !!");
    }
    private native void start0();
}