java第十八课时

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package demo01; import java.util.ArrayList; import java.util.Collection; public class Demo01Collection { 
    public static void main(String[] args) { 
    Collection<String> coll= new ArrayList<>(); System.out.println(coll); boolean b1=coll.add("张三"); System.out.println(b1); System.out.println(coll); coll.add("李四"); coll.add("李四"); coll.add("王五"); coll.add("赵六"); System.out.println(coll); boolean b2=coll.remove("王五"); System.out.println(b2); System.out.println(coll); boolean b3=coll.contains("赵六"); System.out.println(b3); boolean b4=coll.contains("王五"); System.out.println(b4); boolean b5=coll.isEmpty(); System.out.println(b5); int b6=coll.size(); System.out.println(b6); Object[] arr=coll.toArray(); System.out.println(arr[0]); System.out.println("======="); coll.clear(); System.out.println(coll); b5=coll.isEmpty(); System.out.println(b5); } } 

异常分为抛出异常和捕获异常

package Demo02; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class Demo01Exception { 
    public static void main(String[] args) { 
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-mm-dd"); Date date=null; try { 
    date=sdf.parse("2021-05-11"); }catch(ParseException e) { 
    e.printStackTrace(); } System.out.println(date); int[] arr= { 
   1,2,3}; System.out.println(arr[0]); try { 
    System.out.println(arr[2]); }catch(Exception e) { 
    System.out.println("第一句测试"); System.out.println(e); } int[]arr2=new int[1024*1024*1024*1024*1024]; System.out.println("后续代码"); } }