停止读取某一行的文本文件java

Question

在我的程序块中，我试图获取用户输入并将它与文件“PriceList3.txt”中的每一行进行比较。对于每一行，我都存储了一些字符串变量。当其中一行的某些内容与用户输入（contains方法）相同时，我使用Pattern和Matcher类来提取某些信息，并将txt文件的一行部分分配给一个变量。在我调用setPrice方法后，我试图停止阅读“PriceList3.txt”文件。当if（m.find（））中的所有语句都被执行后，您是否知道如何停止读取文件？我不知道从哪里开始。

感谢您的回复和帮助。

String regularExpr = "([\\w]+)\\s+([\\w]+)\\s+([\\d.\\d)]+)[\\D]+([\\d.\\d]+)"; 
Pattern pattern = Pattern.compile(regularExpr); 
File inFile = new File("PriceList3.txt"); 
Scanner read = new Scanner(inFile); 
System.out.print("Enter the name and weight of the item: "); 
String item = scan.nextLine(); 
while(read.hasNextLine()) 
{ 
    String each = read.nextLine(); 
    if(each.contains(item)) 
    { 
     Matcher m = pattern.matcher(each); 
     if(m.find()) 
     { 
      String itemName1 = m.group(1).trim()+ " " + m.group(2); 
      itemName.setName(itemName1); 
      String weight = (m.group(3).trim()); 
      double weight1 = Double.parseDouble(weight); 
      itemName.setWeight(weight1); 
      double itemPrice = Double.parseDouble(m.group(4).trim()); 
      itemName.setPrice(itemPrice); 
     } 
     cashier1.addItem(itemName); 
    } 
} 

Answer 1

你可以使用break语句作为@Neil写，或者你可以检查，而检查的一些变量：

boolean stop = false; 
while(read.hasNextLine() && !stop) { 
... 
//if you want to stop 
stop = true; 

} 

Answer 2

如果你想停止while循环，最简单的是将加休息;

String regularExpr = "([\\w]+)\\s+([\\w]+)\\s+([\\d.\\d)]+)[\\D]+([\\d.\\d]+)"; 
Pattern pattern = Pattern.compile(regularExpr); 
File inFile = new File("PriceList3.txt"); 
Scanner read = new Scanner(inFile); 
System.out.print("Enter the name and weight of the item: "); 
String item = scan.nextLine(); 
while(read.hasNextLine()) 
{ 
    String each = read.nextLine(); 
    if(each.contains(item)) 
    { 
     Matcher m = pattern.matcher(each); 
     if(m.find()) 
     { 
      String itemName1 = m.group(1).trim()+ " " + m.group(2); 
      itemName.setName(itemName1); 
      String weight = (m.group(3).trim()); 
      double weight1 = Double.parseDouble(weight); 
      itemName.setWeight(weight1); 
      double itemPrice = Double.parseDouble(m.group(4).trim()); 
      itemName.setPrice(itemPrice); 
      //Jumps out of the innerst loop 
      break; 
     } 
     cashier1.addItem(itemName); 
    } 
} 
//if break is called, the code will continue at this line 

虽然有些人可能会争辩说破环是不是很好（因为你在代码中跳来跳去，它可以成为大型项目的混乱）。另一种方法是添加布尔值

String regularExpr = "([\\w]+)\\s+([\\w]+)\\s+([\\d.\\d)]+)[\\D]+([\\d.\\d]+)"; 
Pattern pattern = Pattern.compile(regularExpr); 
File inFile = new File("PriceList3.txt"); 
Scanner read = new Scanner(inFile); 
System.out.print("Enter the name and weight of the item: "); 
String item = scan.nextLine(); 
//add the boolean 
boolean complete = false; 
//stops the loop once complete is false 
while(read.hasNextLine() && !complete) 
{ 
    String each = read.nextLine(); 
    if(each.contains(item)) 
    { 
     Matcher m = pattern.matcher(each); 
     if(m.find()) 
     { 
      String itemName1 = m.group(1).trim()+ " " + m.group(2); 
      itemName.setName(itemName1); 
      String weight = (m.group(3).trim()); 
      double weight1 = Double.parseDouble(weight); 
      itemName.setWeight(weight1); 
      double itemPrice = Double.parseDouble(m.group(4).trim()); 
      itemName.setPrice(itemPrice); 
      //Sets the boolean 
      complete = true; 
     } 
     //only adds the item if complete is false 
     if(!complete){ 
      cashier1.addItem(itemName); 
     } 
    } 
}