multithreading - How can I know whether a java Thread is completed when I use Thread class? -

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• how know if other threads have finished? 11 answers

i using multiple thread object , running run() of runnable class downloading images url. how can know t.start() have finished it's work.

my code given below:

class: imagedownloadthread.java

import java.io.fileoutputstream; import java.io.inputstream; import java.io.outputstream; import java.net.url;   public class imagedownloadthread implements runnable{     private string imgurl;     private string destfile;     public imagedownloadthread(string imgurl, string destfile){         this.imgurl = imgurl;         this.destfile = destfile;     }      public void run(){          try{             url url = new url(imgurl);             inputstream = url.openstream();             outputstream os = new fileoutputstream(destfile);             byte[] b = new byte[2048];             int length;             while( (length = is.read(b)) != -1 ){                 os.write(b, 0, length);             }             os.close();             is.close();         } catch (exception e){             e.printstacktrace();         }             }  } 

class: main.java

public class main{      public static void main(string[] args) throws exception {          images images = new images();          int = 0;          (string imstring : images.imageurls) {             imagedownloadthread imagedownloadthread = new imagedownloadthread(imstring, integer.tostring(i) + ".jpg");             thread t = new thread(imagedownloadthread);             t.start();             i++;         }              }  } 

class: images.java

public class images {      public final static string[] imageurls = new string[]{         "https://lh6.googleusercontent.com/-55osaww3x0q/urquutcfr5i/aaaaaaaaabs/rwlj1rukryi/s1024/a%252520photographer.jpg",         "https://lh4.googleusercontent.com/--dq8nirp7w4/urquvgmxvgi/aaaaaaaaabs/-gnulqfnnba/s1024/a%252520song%252520of%252520ice%252520and%252520fire.jpg",         "https://lh5.googleusercontent.com/-7qzedtrkfkc/urquwzt1goi/aaaaaaaaabs/hqwgteynxsg/s1024/another%252520rockaway%252520sunset.jpg",         "https://lh3.googleusercontent.com/--l0km39l5j8/urquxhgcdni/aaaaaaaaabs/3zrsjnrsomq/s1024/antelope%252520butte.jpg",         "https://lh6.googleusercontent.com/-8ho-4vifnlw/urquznsfgti/aaaaaaaaabs/wt8jvitf7vw/s1024/antelope%252520hallway.jpg",         "https://lh4.googleusercontent.com/-wiuwgvcu3qw/urqubrvcj4i/aaaaaaaaabs/yvbwggjwdiq/s1024/antelope%252520walls.jpg",         "https://lh6.googleusercontent.com/-ubmlbpelvoq/urquccdv0ki/aaaaaaaaabs/idnhr2vqoqs/s1024/apre%2525cc%252580s%252520la%252520pluie.jpg",         "https://lh3.googleusercontent.com/-s-afpvgseew/urquc6df-ji/aaaaaaaaabs/mt3xngrud68/s1024/backlit%252520cloud.jpg",         "https://lh5.googleusercontent.com/-bvmif9a9yoq/urquea3hehi/aaaaaaaaabs/rcr6wyeqtao/s1024/bee%252520and%252520flower.jpg",         "https://lh5.googleusercontent.com/-n7mdm7i7fgs/urquet_bt-i/aaaaaaaaabs/9mymxlmpsao/s1024/bonzai%252520rock%252520sunset.jpg",         "https://lh6.googleusercontent.com/-4cn4x4t0m1k/urqufpozwzi/aaaaaaaaabs/8wk41lg1kps/s1024/caterpillar.jpg",         "https://lh3.googleusercontent.com/-rrfnvc8xqeg/urqufdrlbai/aaaaaaaaabs/s69wyy_fl1e/s1024/chess.jpg",         "https://lh5.googleusercontent.com/-wvprptwh8yw/urqugh-qmdi/aaaaaaaaabs/e-mgbgtluwu/s1024/chihuly.jpg",         "https://lh5.googleusercontent.com/-0bdxkymckbo/urquhkfw84i/aaaaaaaaabs/ogqthctk2jq/s1024/closed%252520door.jpg",         "https://lh3.googleusercontent.com/-pyggxxzrykm/urquh-kvvoi/aaaaaaaaabs/hftdwhtrhhq/s1024/colorado%252520river%252520sunset.jpg",         "https://lh3.googleusercontent.com/-zas4dnztalc/urquikvocwi/aaaaaaaaabs/dxz4h3dll1y/s1024/colors%252520of%252520autumn.jpg",         "https://lh4.googleusercontent.com/-gztnweiimz8/urqukvcu7bi/aaaaaaaaabs/jo2hjv6mz6m/s1024/countryside.jpg",         "https://lh4.googleusercontent.com/-beg9ez9qoim/urquklz3fgi/aaaaaaaaabs/uuuv8ac2bae/s1024/death%252520valley%252520-%252520dunes.jpg",         "https://lh6.googleusercontent.com/-ijqj8w68tee/urqulgkvfei/aaaaaaaaabs/zpxviwi_rfw/s1024/delicate%252520arch.jpg",         "https://lh5.googleusercontent.com/-oh8mmy2ieng/urqulldwehi/aaaaaaaaabs/tbdeefsaizy/s1024/despair.jpg",         "https://lh5.googleusercontent.com/-gl0y4uiaolk/urqumc_kjbi/aaaaaaaaabs/pm1et7dn4oo/s1024/eagle%252520fall%252520sunrise.jpg",         "https://lh3.googleusercontent.com/-hyyhd2_vxpq/urqumtja9ei/aaaaaaaaabs/waalxvkbsh0/s1024/electric%252520storm.jpg",         "https://lh5.googleusercontent.com/-pyy_yiyjpto/urqunuohhfi/aaaaaaaaabs/azzoulnujxc/s1024/false%252520kiva.jpg",         "https://lh6.googleusercontent.com/-pyvlvdvxywk/urqunwd8hfi/aaaaaaaaabs/qimwgkfvf6i/s1024/fitzgerald%252520streaks.jpg",         "https://lh4.googleusercontent.com/-kir_uobiiqy/urquocz9sli/aaaaaaaaabs/y4d4q8sxu4c/s1024/foggy%252520sunset.jpg",         "https://lh6.googleusercontent.com/-9lzok_owzh0/urquoo4xyoi/aaaaaaaaabs/awgzhtnvcwu/s1024/frantic.jpg",         "https://lh3.googleusercontent.com/-0x3jnakaz48/urquph78wpi/aaaaaaaaabs/lhxxu_zbh8s/s1024/golden%252520gate%252520afternoon.jpg",         "https://lh6.googleusercontent.com/-95sb5ag7abc/urqupl95rdi/aaaaaaaaabs/g73r20ivtra/s1024/golden%252520gate%252520fog.jpg",         "https://lh3.googleusercontent.com/-jb9v6rtghhk/urqup21f-zi/aaaaaaaaabs/64fb8qmzwxk/s1024/golden%252520grass.jpg",         "https://lh4.googleusercontent.com/-eibgfnultii/urquqvhwari/aaaaaaaaabs/fa4mcv2u8ve/s1024/grand%252520teton.jpg",         "https://lh4.googleusercontent.com/-womxzvmn9ny/urquq1v2aoi/aaaaaaaaabs/grj5umhl6na/s1024/grass%252520closeup.jpg",         "https://lh3.googleusercontent.com/-6hziehxx64q/urqurxvndqi/aaaaaaaaabs/kwmxm3o5ovi/s1024/green%252520grass.jpg",         "https://lh5.googleusercontent.com/-6lvb9oxtq60/urqutebfuki/aaaaaaaaabs/4f4krgecwfs/s1024/hanging%252520leaf.jpg",         "https://lh4.googleusercontent.com/-zavf__52onk/urqutt_iuxi/aaaaaaaaabs/d_bcuc0thou/s1024/highway%2525201.jpg",         "https://lh6.googleusercontent.com/-h4srug615ra/urquul27fxi/aaaaaaaaabs/4aeqjfimsou/s1024/horseshoe%252520bend%252520sunset.jpg",         "https://lh4.googleusercontent.com/-jhfi4fb_pqw/urquux-qxbi/aaaaaaaaabs/ixpyuxuweym/s1024/horseshoe%252520bend.jpg",         "https://lh5.googleusercontent.com/-uggssvfrj7g/urquueyjzgi/aaaaaaaaabs/yyibllt0tom/s1024/into%252520the%252520blue.jpg",         "https://lh3.googleusercontent.com/-ch7koupi7ui/urquu0ff__i/aaaaaaaaabs/r7gdmi7v_g0/s1024/jelly%252520fish%2525202.jpg",         "https://lh4.googleusercontent.com/-pwuuw6yhg8u/urquvpxr3fi/aaaaaaaaabs/vngk6f-tsge/s1024/jelly%252520fish%2525203.jpg",         "https://lh5.googleusercontent.com/-gouqvw1fnfw/urquv6xbc0i/aaaaaaaaabs/zeuvtqq43zc/s1024/kauai.jpg",         "https://lh6.googleusercontent.com/-8qdyyqepyjw/urquwvdh88i/aaaaaaaaabs/cktdy-ysfho/s1024/kyoto%252520sunset.jpg",         "https://lh4.googleusercontent.com/-vpeekydjoe0/urquwzj28qi/aaaaaaaaabs/qxcyxulszrg/s1024/lake%252520tahoe%252520colors.jpg",         "https://lh4.googleusercontent.com/-xbpxwpd4yxu/urquxwhk8ai/aaaaaaaaabs/ardpedypimy/s1024/lava%252520from%252520the%252520sky.jpg",         "https://lh3.googleusercontent.com/-897vxrjb6re/urquxxxd-5i/aaaaaaaaabs/j-cz4t4yviw/s1024/leica%25252050mm%252520summilux.jpg",         "https://lh5.googleusercontent.com/-qsj4d4ixzgo/urquydwij1i/aaaaaaaaabs/k2pbxewehoa/s1024/leica%25252050mm%252520summilux.jpg",         "https://lh6.googleusercontent.com/-dwlpg83vzlg/urquyltvufi/aaaaaaaaabs/g6syq8b4ysi/s1024/leica%252520m8%252520%252528front%252529.jpg",         "https://lh3.googleusercontent.com/-r3_eyayjvfk/urquzqbv8ei/aaaaaaaaabs/b9xhpum3pei/s1024/light%252520to%252520sand.jpg",         "https://lh3.googleusercontent.com/-fhy5h67qpi0/urqu0cp4j1i/aaaaaaaaabs/0lg6m94z6vm/s1024/little%252520bit%252520of%252520paradise.jpg",         "https://lh5.googleusercontent.com/-tzf_lwrcnrm/urqu0rddpoi/aaaaaaaaabs/gaj2dliux0s/s1024/lone%252520pine%252520sunset.jpg",         "https://lh3.googleusercontent.com/-4hdpj4_dxu4/urqu046dj9i/aaaaaaaaabs/eboodtk2_uk/s1024/lonely%252520rock.jpg",         "https://lh6.googleusercontent.com/-erbf--z-w4s/urqu1ajslki/aaaaaaaaabs/xjdcdo1inzm/s1024/longue%252520vue.jpg",         "https://lh6.googleusercontent.com/-0cxjrdjaqvc/urqu1opnzni/aaaaaaaaabs/pfb2opuu7lk/s1024/look%252520me%252520in%252520the%252520eye.jpg",         "https://lh3.googleusercontent.com/-d_5lnxndn6g/urqu2tk7hvi/aaaaaaaaabs/p0ddca9w__y/s1024/lost%252520in%252520a%252520field.jpg",         "https://lh6.googleusercontent.com/-flsqwmrik2q/urqu24pcmji/aaaaaaaaabs/5ocih85xofm/s1024/marshall%252520beach%252520sunset.jpg",         "https://lh4.googleusercontent.com/-y4lgryevtmu/urqu28kg3gi/aaaaaaaaabs/ojxpekqtbj4/s1024/mono%252520lake%252520blue.jpg",         "https://lh4.googleusercontent.com/-aahajpmcgya/urqu3pildhi/aaaaaaaaabs/lctqk1sicrs/s1024/monument%252520valley%252520overlook.jpg",         "https://lh4.googleusercontent.com/-vkxfdq83dqa/urqu31yq_bi/aaaaaaaaabs/ouogk_2ayfm/s1024/moving%252520rock.jpg",         "https://lh5.googleusercontent.com/-cg62qippwxg/urqu4ia4vri/aaaaaaaaabs/0yodqlalcac/s1024/napali%252520coast.jpg",         "https://lh6.googleusercontent.com/-wdgrp5pmmjq/urqu5pzvn7i/aaaaaaaaabs/m0abecdpxe4/s1024/one%252520wheel.jpg",         "https://lh6.googleusercontent.com/-6ws5docguoa/urqu5qx1ugi/aaaaaaaaabs/gimw2ixpvry/s1024/open%252520sky.jpg",         "https://lh6.googleusercontent.com/-u8ehkj8g8gq/urqu55sm6yi/aaaaaaaaabs/lixx_gltdmi/s1024/orange%252520sunset.jpg",         "https://lh6.googleusercontent.com/-74z5qj4btde/urqu6lsrjri/aaaaaaaaabs/xzmvkw90szq/s1024/orchid.jpg",         "https://lh6.googleusercontent.com/-leqe4h6tepe/urqu6t_lski/aaaaaaaaabs/zvgykoea_qy/s1024/over%252520there.jpg",         "https://lh5.googleusercontent.com/-cauh-53jh2m/urqu66v_usi/aaaaaaaaabs/eucwwqclfkq/s1024/plumes.jpg",         "https://lh3.googleusercontent.com/-edlt2jhdoy4/urqu7axzkai/aaaaaaaaabs/ivze-xj7lzs/s1024/rainbokeh.jpg",         "https://lh5.googleusercontent.com/-j1nlqefiyco/urqu8l1cgci/aaaaaaaaabs/aqzkgx66zli/s1024/rainbow.jpg",         "https://lh5.googleusercontent.com/-drnqmk0t4vu/urqu8xyn9yi/aaaaaaaaabs/lgvf_592wlu/s1024/rice%252520fields.jpg",         "https://lh3.googleusercontent.com/-hwh1v3eogcq/urqu8qoakwi/aaaaaaaaabs/iljrjrnbjgw/s1024/rockaway%252520fire%252520sky.jpg",         "https://lh5.googleusercontent.com/-wjv6fqk7tlk/urqu9jcq8si/aaaaaaaaabs/ryyupdo-c9o/s1024/rockaway%252520flow.jpg",         "https://lh6.googleusercontent.com/-6caxnfo7d20/urqu-bdzgpi/aaaaaaaaabs/omsyllzjqwo/s1024/rockaway%252520sunset%252520sky.jpg",         "https://lh3.googleusercontent.com/-sl8fpgps-re/urqu_bokfgi/aaaaaaaaabs/dg2fv-jxoeg/s1024/russian%252520ridge%252520sunset.jpg",         "https://lh6.googleusercontent.com/-gvty36mmbig/urqu_q91lki/aaaaaaaaabs/3cifmbcy5ma/s1024/rust%252520knot.jpg",         "https://lh6.googleusercontent.com/-gheimuhqjbe/urqu_fkfvli/aaaaaaaaabs/axuejeqam7q/s1024/sailing%252520stones.jpg",         "https://lh3.googleusercontent.com/-hbbyzjtowgc/urqu_ycpiri/aaaaaaaaabs/nadjuxngjye/s1024/seahorse.jpg",         "https://lh3.googleusercontent.com/-iwi6-i6iexy/urqvayzhsvi/aaaaaaaaabs/5etwl4qxsfe/s1024/shinjuku%252520street.jpg",         "https://lh6.googleusercontent.com/-amhnystm_my/urqvalb5koi/aaaaaaaaabs/pfcfgzlksn0/s1024/sierra%252520heavens.jpg",         "https://lh5.googleusercontent.com/-djgjepfryso/urqvbvjzrai/aaaaaaaaabs/v-f5qwpyo6s/s1024/sierra%252520sunset.jpg",         "https://lh4.googleusercontent.com/-z4zgic5nwdc/urqvbdewivi/aaaaaaaaabs/zrzr1vj84qa/s1024/sin%252520lights.jpg",         "https://lh4.googleusercontent.com/-_0cyiww8ccy/urqvbz3im4i/aaaaaaaaabs/9n_wq8mhlty/s1024/starry%252520lake.jpg",         "https://lh3.googleusercontent.com/-a9lmoryuqua/urqvcyx_joi/aaaaaaaaabs/s7sde1bz9ci/s1024/starry%252520night.jpg",         "https://lh3.googleusercontent.com/-ktlj3k858ey/urqvc_2h_bi/aaaaaaaaabs/zzebimwda_g/s1024/stream.jpg",         "https://lh5.googleusercontent.com/-dfb7lad6rca/urqvduftwwi/aaaaaaaaabs/brhoutxtn7o/s1024/strip%252520sunset.jpg",         "https://lh5.googleusercontent.com/-at6apgfin20/urqvdyffuzi/aaaaaaaaabs/clabcx171be/s1024/sunset%252520hills.jpg",         "https://lh4.googleusercontent.com/-7-ehhtqthii/urqveytk4vi/aaaaaaaaabs/qsjzob3yjvg/s1024/tenaya%252520lake%2525202.jpg",         "https://lh6.googleusercontent.com/-8mrjv_a-pok/urqvfc5repi/aaaaaaaaabs/9inktg9fbce/s1024/tenaya%252520lake.jpg",         "https://lh5.googleusercontent.com/-b1hw-z4zwao/urqvfwyrwui/aaaaaaaaabs/8peli53bs8i/s1024/the%252520cave%252520bw.jpg",         "https://lh3.googleusercontent.com/-po4e-xzkanq/urqvgrqjyki/aaaaaaaaabs/42nyadfsxag/s1024/the%252520fisherman.jpg",         "https://lh4.googleusercontent.com/-ilyzlzfdy7s/urqvg0yscdi/aaaaaaaaabs/1j9edkmkxtk/s1024/the%252520night%252520is%252520coming.jpg",         "https://lh6.googleusercontent.com/-g-k7ykkuco0/urqvhhah6fi/aaaaaaaaabs/_taqqg7t0vo/s1024/the%252520road.jpg",         "https://lh6.googleusercontent.com/-h-aljt7ksus/urqvithqyfi/aaaaaaaaabs/ejiv35olws8/s1024/tokyo%252520heights.jpg",         "https://lh5.googleusercontent.com/-hy9k-tbs7xg/urqvijqmoxi/aaaaaaaaabs/rspmmoatskg/s1024/tokyo%252520highway.jpg",         "https://lh6.googleusercontent.com/-83oovmb4ozs/urqvjl0t7li/aaaaaaaaabs/c5tecz6ronm/s1024/tokyo%252520smog.jpg",         "https://lh3.googleusercontent.com/-fb-jfgreefi/urqvji3exai/aaaaaaaaabs/xfyweirf4v8/s1024/tufa%252520at%252520night.jpg",         "https://lh4.googleusercontent.com/-vngkd5z1u8w/urqvjucegpi/aaaaaaaaabs/ulxcmvcu6eu/s1024/valley%252520sunset.jpg",         "https://lh6.googleusercontent.com/-doz5i2e2omq/urqvkmnd1ki/aaaaaaaaabs/iqf0isinleo/s1024/windmill%252520sunrise.jpg",         "https://lh5.googleusercontent.com/-biyiywcj9mu/urqvkculiai/aaaaaaaaabs/jypscpljope/s1024/windmill.jpg",         "https://lh4.googleusercontent.com/-pdt167_xrda/urqvk36mlci/aaaaaaaaabs/oi2ik9qsemi/s1024/windmills.jpg",         "https://lh5.googleusercontent.com/-ki_qdyx7vlu/urqvlxcb6gi/aaaaaaaaabs/n31vlz6u89o/s1024/yet%252520another%252520rockaway%252520sunset.jpg",         "https://lh4.googleusercontent.com/-e9nhz5k5mss/urqvmibzjti/aaaaaaaaabs/1fv810rdnfq/s1024/yosemite%252520tree.jpg",};  } 

you can use thread.alive() method.