Java updates

code/ArrayAdd.java

@@ -2,7 +2,7 @@
 
 class ArrayAdd {
   public static void main(String[] args) {
-    List<String> arr = new ArrayList<String>();
+    List<String> arr = new ArrayList<>();
     arr.add("first");
     arr.add("second");
     System.out.println(arr);

code/ArrayConcat.java

@@ -4,7 +4,7 @@ class ArrayConcat {
   public static void main(String[] args) {
     List<Integer> arr1 = Arrays.asList(1, 2);
     List<Integer> arr2 = Arrays.asList(3, 4);
-    List<Integer> concated = new ArrayList<Integer>(arr1);
+    List<Integer> concated = new ArrayList<>(arr1);
     concated.addAll(arr2);
     System.out.println(concated);
   }

code/ArrayCount.java

@@ -3,10 +3,6 @@
 class ArrayCount {
   public static void main(String[] args) {
     List<Integer> arr = Arrays.asList(1, 11, 111);
-    int count = 0;
-    for (int n : arr)
-      if (n > 10)
-        count++;
-    System.out.println(count);
+    System.out.println(arr.stream().count());
   }
 }

code/ArrayDeleteElement.java

@@ -2,12 +2,8 @@
 
 class ArrayDeleteElement {
   public static void main(String[] args) {
-    List<String> arr = new LinkedList<String>(Arrays.asList("a", "b", "c"));
-    Iterator<String> iter = arr.iterator();
-    while(iter.hasNext()) {
-      if(iter.next().equalsIgnoreCase("b"))
-        iter.remove();
-    }
+    List<String> arr = new LinkedList<>(Arrays.asList("a", "b", "c"));
+    arr.removeIf(str -> str.equalsIgnoreCase("b"));
     System.out.println(arr);
   }
 }

code/ArrayFind.java

@@ -3,13 +3,7 @@
 class ArrayFind {
   public static void main(String[] args) {
     List<Integer> arr = Arrays.asList(1, 5, 10, 20);
-    int first = 0;
-    for (int n : arr) {
-      if (n % 2 == 0) {
-        first = n;
-        break;
-      }
-    }
+    int first = arr.stream().filter(n -> n % 2 == 0).findFirst().get();
     System.out.println(first);
   }
 }

code/ArrayIterate.java

@@ -1,9 +1,7 @@
-import java.util.*;
+import java.util.Arrays;
 
 class ArrayIterate {
   public static void main(String[] args) {
-    for (int num : Arrays.asList(1, 2)) {
-      System.out.println(num);
-    }
+    Arrays.asList(1, 2).stream().sequential().forEach(System.out::println);
   }
 }

code/ArrayMap.java

@@ -1,11 +1,10 @@
 import java.util.*;
+import java.util.stream.Collectors;
 
 class ArrayMap {
   public static void main(String[] args) {
-    List<Integer> arr = Arrays.asList(1, 5, 10, 20);
-    List<Integer> mapped = new ArrayList<Integer>();
-    for (int n : arr)
-      mapped.add(n * 2);
+    List<Integer> arr    = Arrays.asList(1, 5, 10, 20);
+    List<Integer> mapped = arr.stream().map(n -> n * 2).collect(Collectors.toList());
     System.out.println(mapped);
   }
 }

code/ArrayMulti.java

@@ -2,7 +2,7 @@
 
 class ArrayMulti {
   public static void main(String[] args) {
-    List<List<String>> arr = new ArrayList<List<String>>();
+    List<List<String>> arr = new ArrayList<>();
     arr.add(Arrays.asList("first", "second"));
     arr.add(Arrays.asList("third", "forth"));
     System.out.println(arr.get(1).get(1));

code/ArrayReduce.java

@@ -1,10 +1,8 @@
-import java.util.*;
+import java.util.stream.IntStream;
 
 class ArrayReduce {
   public static void main(String[] args) {
-    int sum = 0;
-    for (int n : Arrays.asList(1, 2, 3))
-      sum += n;
+    int sum = IntStream.of(1, 2, 3).sum();
     System.out.println(sum);
   }
 }

code/ArraySelect.java

@@ -1,12 +1,10 @@
 import java.util.*;
+import java.util.stream.Collectors;
 
 class ArraySelect {
   public static void main(String[] args) {
     List<Integer> arr = Arrays.asList(1, 5, 10, 20);
-    List<Integer> all = new ArrayList<Integer>();
-    for (int n : arr)
-      if (n % 2 == 0)
-        all.add(n);
+    List<Integer> all = arr.stream().filter(n -> n % 2 == 0).collect(Collectors.toList());
     System.out.println(all);
   }
 }

code/FileRead.java

@@ -1,18 +1,12 @@
 import java.io.*;
+import java.util.stream.Collectors;
 
 class FileRead {
   public static void main(String[] args) throws IOException {
     String filePath = System.getProperty("user.dir") + "/code/file.txt";
     String content;
     try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
-      StringBuilder sb = new StringBuilder();
-      String line = br.readLine();
-      while (line != null) {
-        sb.append(line);
-        sb.append(System.lineSeparator());
-        line = br.readLine();
-      }
-      content = sb.toString();
+      content = br.lines().collect(Collectors.joining(System.lineSeparator()))+System.lineSeparator();
     }
     System.out.println(content);
   }

code/HashAdd.java

@@ -2,7 +2,7 @@
 
 class HashAdd {
   public static void main(String[] args) {
-    Map<String, String> options = new HashMap<String, String>();
+    Map<String, String> options = new HashMap<>();
     options.put("fontSize", "10");
     options.put("fontFamily", "Arial");
     System.out.println(options);

code/LoopFor.java

@@ -1,6 +1,7 @@
+import java.util.stream.IntStream;
+
 class LoopFor {
   public static void main(String[] args) {
-    for (int i = 1; i <= 3; i++)
-      System.out.println(i + ". Hi");
+    IntStream.range(1, 3+1).sequential().mapToObj(i -> i + ". Hi").forEach(System.out::println);
   }
 }

code/LoopNext.java

@@ -1,9 +1,11 @@
+import java.util.stream.IntStream;
+
 class LoopNext {
   public static void main(String[] args) {
-    for (int i = 0; i < 3; i++) {
-      if (i == 1)
-        continue;
-      System.out.println((i + 1) + ". Hi");
-    }
+    IntStream.range(0, 3)
+      .sequential()
+      .filter(i -> i != 1)
+      .mapToObj(i -> (i + 1) + ". Hi")
+      .forEach(System.out::println);
   }
 }

code/LoopTimes.java

@@ -1,6 +1,7 @@
+import java.util.stream.IntStream;
+
 class LoopTimes {
   public static void main(String[] args) {
-    for (int i = 0; i < 3; i++)
-      System.out.println("Hi");
+    IntStream.range(0, 3).sequential().mapToObj(i -> "Hi").forEach(System.out::println);
   }
 }

code/LoopUntil.java

@@ -1,8 +1,8 @@
+import java.util.stream.IntStream;
+
 class LoopUntil {
   public static void main(String[] args) {
-    int i = 0;
-    while (i != 3)
-      i++;
+    int i = IntStream.iterate(0, n -> n + 1).filter(n -> n == 3).findFirst().getAsInt();
     System.out.println(i);
   }
 }

code/OtherRunCommand.java

@@ -1,17 +1,16 @@
 import java.io.*;
+import java.util.stream.Collectors;
 
 class OtherRunCommand {
   public static void main(String[] args) throws IOException, InterruptedException {
-    String result = "";
+    final String result;
     ProcessBuilder ps = new ProcessBuilder("java", "-version");
     ps.redirectErrorStream(true);
     Process pr = ps.start();
-    BufferedReader in = new BufferedReader(new InputStreamReader(pr.getInputStream()));
-    String line;
-    while ((line = in.readLine()) != null)
-      result += line + "\n";
-    pr.waitFor();
-    in.close();
+    try (BufferedReader in = new BufferedReader(new InputStreamReader(pr.getInputStream()))) {
+      result = in.lines().collect(Collectors.joining("\n"));
+      pr.waitFor();
+    }
     System.out.println(result);
   }
 }

code/TypeNullTrueFalse.java

@@ -8,7 +8,7 @@ public static void main(String[] args) {
     String shouldBeNull = null;
     System.out.println(shouldBeNull == null);
 
-    List<String> arr = new ArrayList<String>();
+    List<String> arr = new ArrayList<>();
     System.out.println(arr.isEmpty());
   }
 }