🚀Add eclipse project files

Changes to be committed:
            new file:   .classpath
            new file:   .project
            new file:   .settings/org.eclipse.jdt.core.prefs

Author: yansheng836

.classpath

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src/main/example1_5"/>
+	<classpathentry kind="src" path="src/main/example6_9"/>
+	<classpathentry kind="src" path="src/main/example10_12"/>
+	<classpathentry kind="src" path="src/main/example13_15"/>
+	<classpathentry kind="src" path="src/main/practice1_9"/>
+	<classpathentry kind="src" path="src/main/practice10_15"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/jdk1.8.0-144"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>java-textbook-source</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.8