Question

如何使用缓冲的Reader或Scanner从java中的文本文件中读取前5行？这是我的代码

        final int assumedLineLength = 16;


    File file = new File("src/hw7p1/Acronyms.txt");
     HashMap<String, String> hashMap = new HashMap<String, String>((int)(file.length() / assumedLineLength) * 2);
    BufferedReader reader = null;
    int linecount = 0 ;
    String eachLine = null;
    try {
    reader = new BufferedReader(new FileReader(file));

    for ( eachLine = reader.readLine(); 
            eachLine != null; 
            eachLine = reader.readLine()) {
        hashMap.put(eachLine, " ");
        linecount++; int i = 0;

    }


    TreeMap<String, String> sorted = new TreeMap<>(hashMap);

     Set<Entry<String, String>> sortings = sorted.entrySet();

    for(Entry<String, String> sort : sortings){ 
        System.out.println(sort.getKey() + " " + sort.getValue());

    }

     }catch (IOException e) {
         e.printStackTrace();
     }

} 它打印出文本文件，但我想要做的只是让它打印出前5行。任何帮助，将不胜感激。

Answer 1

在for循环中，如果只需要5行，请不要使用eachLine。使用

import UIKit

class ContactosViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

let defaultValues = UserDefaults.standard

var contactos: String = ""
var numerosmov: String = ""
var tablacontacto = [String] ()
var tablanumero = [String] ()

let cellIdentifier: String = "cell"
let cellIdentifier2: String = "cell2"


@IBOutlet weak var contactoTable: UITableView!
@IBOutlet weak var numTable: UITableView!


override func viewDidLoad() {
    super.viewDidLoad()

    let backButton = UIBarButtonItem(title: "", style: UIBarButtonItemStyle.plain, target: navigationController, action: nil)
    navigationItem.leftBarButtonItem = backButton

    // Do any additional setup after loading the view.

    datosRecividos(contactos, numerosmov)
    contactoTable.delegate = self
    numTable.delegate = self
    contactoTable.dataSource = self
    numTable.dataSource = self
    contactoTable!.reloadData()
    numTable!.reloadData()
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)
    contactoTable.reloadData()
    numTable.reloadData()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func datosRecividos(_ contactosr: String, _ numerosr: String)
{
tablacontacto.append(contactosr)
    tablanumero.append(numerosr)
    let usercontacto = defaultValues.array(forKey: "contactoTable")
    let usernumero = defaultValues.array(forKey: "numeroTable")

}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if (tableView.tag == 1)
    {
    return(tablacontacto.count)
    }
    else if (tableView.tag == 2)
    {
    return(tablanumero.count)
    }
    return 0
}


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifier, for: indexPath)

    if (tableView.tag == 1)
    {
    cell.textLabel?.text = tablacontacto[indexPath.row] as! String

    }
    else if (tableView.tag == 2)
    {
       cell.textLabel?.text = tablanumero[indexPath.row] as! String

    }

    return(cell)
}





}

Answer 2

public String[] readLines(int noLines, String path) throws IOException {

     FileReader fr = new FileReader(path);
     BufferedReader br = new BufferedReader(fr);
     String[] textData = new String[noLines];

     int i;

     for (i=0; i < noLines; i++) {

         textData[i] = br.readLine();

     }

     br.close( );

     return textData;

 }

如何从文本文件中读取5行

2 个答案: