Java开发简要，java开发

public class Test{

    public static void main(String[] args){
        
        system.out.println("hello world");
    }
}

注释

关键字

JAVA关键字

部分重要的关键字

数据类型

引用数据类型：类、接口、数组

变量作用范围和默认初值

内部类：类的嵌套定义

多线程：在一个进程中有多个顺序流同时执行

异常(Exception)

非运行时异常：    除了运行时异常之外的其他由Exception继承来的异常。

String类

public class Test {

	public static void main(String[] args) {
		
		String str1 = new String("hello");
		String str2 = new String("hello");
		
		String str3 = "hello";
		String str4 = "hello";
		
		System.out.println(str1==str2);
		System.out.println(str3==str4);
		System.out.println(str1.equals(str2));
		System.out.println(str3.equals(str1));
		System.out.println(str3.equals(str4));
	
		String s = "hello ";
		String ss = "how are you ?";
		String sss = "    he  llo   ";
		System.out.println("从指定位置查找第一个字符l的位置: "+s.indexOf('l',0));
		System.out.println("查找最后一个字符l的位置: "+s.lastIndexOf('l'));
		System.out.println("截取指定位置的字符串: "+s.substring(1, 4));
		System.out.println("字符串拼接: "+s.concat(ss));
		System.out.println("替换指定字符: "+s.replace('e', 'a'));
		System.out.println(sss.trim());//去掉指定空格
	}
}

对象集合的接口

IO

public class Util {
/**
 * cpFile1复制文本文件
 * cpFile2复制图片和音频文件
 * @param startFile 要复制的文件
 * @param endFile	复制后生成的文件
 */
	public static void cpFile1(String startFile, String endFile) {

		BufferedReader bufferedReader = null;
		BufferedWriter bufferedWriter = null;
		
		try {	
			bufferedReader = new BufferedReader(new FileReader(new File(startFile)));
			bufferedWriter = new BufferedWriter(new FileWriter(new File(endFile)));		 
			String buf = null;
			while((buf = bufferedReader.readLine())!= null) {				
				bufferedWriter.write(buf);
				bufferedWriter.newLine();
			}
		} catch (FileNotFoundException e){
			// TODO Auto-generated catch block	
			e.printStackTrace();		
		} catch (IOException e) {
			// TODO Auto-generated catch block	
			e.printStackTrace();		
		}finally {		
			try {			
				bufferedReader.close();
				bufferedWriter.close();			
			} catch (IOException e) {
				// TODO Auto-generated catch block				
				e.printStackTrace();
			}
		}
	}
	
	public static void cpFile2(String startFile, String endFile) {
		
		BufferedInputStream bufferedInputStream = null;
		BufferedOutputStream bufferedOutputStream = null;
		
		try {	
			bufferedInputStream = new BufferedInputStream(new FileInputStream(new File(startFile)));
			bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(new File(endFile)));	
			int i = 0;			
			while((i = bufferedInputStream.read()) != -1){
				bufferedOutputStream.write(i);
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{			
			try {
				bufferedInputStream.close();
				bufferedOutputStream.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

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