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  • 常用类demo--【J2SE】

    StringBuffer类

    		public class TestStringBuffer{
    			public static void main(String[] args){
    				String s="Mircosoft";
    				char[] a={'a' ,'b' ,'c'};
    				StringBuffer sb1=new StringBuffer(s);
    				sb1.append('/').append("IBM").append('/').append("Sun");
    				System.out.println(sb1);
    				StringBuffer sb2=new StringBuffer("数字");
    				for (int i=0;i<=9;i++){
    					sb2.append(i);
    				}
    				System.out.println(sb2);
    				sb2.delete(8,sb2.length());
    				System.out.println(sb2);
    				System.out.println(sb2.reverse());
    			}
    		
    
    }
    

     

    Stringbuffer是可变的,String是不可变的。

    File类

    		import java.io.*;
    		//把所有的孩子的递归都列出来
    		public class FileList{
    			public static void main(String[] args){
    				File f=new File("d:/A");
    				tree(f);
    			}
    			private static void tree(File f){
    				File[] childs=f.listFiles();
    				for(int i =0;i<childs.length;i++){
    					System.out.println(childs[i].getName());
    					if(childs[i].isDirectory()){
    						tree(childs[i]);
    					}
    				}
    			}
    		}
    

    枚举类型:

    		public class TestEnum{
    			
    			public enum MyColor{red,green,blue};
    		
    			
    			public static void main(String[] args){
    				MyColor m=MyColor.red;
    				switch(m){
    						case red:
    						System.out.println("red");
    						break;
    						case green:
    							System.out.println("green");
    							break;
    						default:
    							System.out.println("default");			
    				}
    				
    				System.out.println(m);
    			}
    		}
    

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  • 原文地址:https://www.cnblogs.com/wangmei/p/4822327.html
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