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<pre class="code-text" style="margin:0;background:none;border:none;font:inherit;line-height:inherit;padding:0;overflow:visible"><code style="background:none;border:none;padding:0;font:inherit">public class Point {
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public record Circle(double r)
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Square(double side) {
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public boolean test(String s) {..}
};</span>
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default void logInfo(String msg) {
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private String format(String lvl, String msg) {
return "[" + lvl + "] " + timestamp() + msg;
}
default void logInfo(String msg) {
System.out.println(format("INFO", msg));
}
default void logWarn(String msg) {
System.out.println(format("WARN", msg));
}
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else if (obj instanceof Double d)
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else if (obj instanceof String s)
return "str: " + s;
return "unknown";
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return switch (obj) {
case Integer i -> "int: " + i;
case Double d -> "double: " + d;
case String s -> "str: " + s;
default -> "unknown";
};
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<span class="code-text">if (shape instanceof Circle c) {
if (c.radius() > 10) {
return "large circle";
} else {
return "small circle";
}
} else {
return "not a circle";
}</span>
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<span class="code-text">return switch (shape) {
case Circle c
when c.radius() > 10
-> "large circle";
case Circle c
-> "small circle";
default -> "not a circle";
};</span>
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<h3>Primitive types in patterns</h3>
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<span class="code-text">String classify(int code) {
if (code >= 200 && code < 300)
return "success";
else if (code >= 400 && code < 500)
return "client error";
else
return "other";
}</span>
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<span class="code-text">String classify(int code) {
return switch (code) {
case int c when c >= 200
&& c < 300 -> "success";
case int c when c >= 400
&& c < 500 -> "client error";
default -> "other";
};
}</span>
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<h3>Module import declarations</h3>
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<span class="code-text">import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;</span>
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<span class="code-text">import module java.base;
// All of java.util, java.io, java.nio
// etc. available in one line</span>
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<span class="code-text">// Must add default even though
// all cases are covered
double area(Shape s) {
if (s instanceof Circle c)
return Math.PI * c.r() * c.r();
else if (s instanceof Rect r)
return r.w() * r.h();
else throw new IAE();
}</span>
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<span class="code-text">// sealed Shape permits Circle, Rect
double area(Shape s) {
return switch (s) {
case Circle c ->
Math.PI * c.r() * c.r();
case Rect r ->
r.w() * r.h();
}; // no default needed!
}</span>
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<h3>Immutable list creation</h3>
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<span class="code-text">List<String> list =
Collections.unmodifiableList(
new ArrayList<>(
Arrays.asList("a", "b", "c")
)
);</span>
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<span class="code-text">List<String> list =
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<span class="code-text">Map<String, Integer> map = new HashMap<>();
map.put("a", 1);
map.put("b", 2);
map.put("c", 3);
map = Collections.unmodifiableMap(map);</span>
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<h3>Immutable set creation</h3>
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<span class="code-text">Set<String> set =
Collections.unmodifiableSet(
new HashSet<>(
Arrays.asList("a", "b", "c")
)
);</span>
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<span class="code-text">Set<String> set =
Set.of("a", "b", "c");</span>
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<h3>Copying collections immutably</h3>
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<span class="code-text">List<String> copy =
Collections.unmodifiableList(
new ArrayList<>(original)
);</span>
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<span class="code-text">List<String> copy =
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<h3>Map.entry() factory</h3>
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<span class="code-text">Map.Entry<String, Integer> e =
new AbstractMap.SimpleEntry<>(
"key", 42
);</span>
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<span class="code-text">// Get last element
var last = list.get(list.size() - 1);
// Get first