diff --git a/jaehong/chapter7/ManageHeight.java b/jaehong/chapter7/ManageHeight.java
new file mode 100644
index 0000000..c109562
--- /dev/null
+++ b/jaehong/chapter7/ManageHeight.java
@@ -0,0 +1,61 @@
+import java.util.*;
+import java.util.stream.*;
+public class ManageHeight{
+
+	private int[][] gradeHeights = new int[5][];
+
+	public static void main(String...args){
+		final var manageHeight = new ManageHeight();
+		manageHeight.setData();
+
+		manageHeight.printHeight();
+		manageHeight.printAverage();
+	}
+
+	public void setData(){
+		this.insert(1, new int[]{170,180,173,175,177});
+		this.insert(2, new int[]{160,165,167,186 });
+		this.insert(3, new int[]{158,177,187,176});
+		this.insert(4, new int[]{173, 182,181});
+		this.insert(5, new int[]{170,180,165,177,172});
+	}
+	private void insert(int grade, int[] heights){
+		this.gradeHeights[grade - 1] = heights;
+	}
+
+	public void printHeight(){
+		System.out.println("결과");
+		IntStream.range(0, gradeHeights.length).forEach(this::printHeight);
+	}
+
+	public void printHeight(int classNo){
+		var grade = gradeHeights[classNo];
+		var sb = new StringBuilder();
+
+		sb.append(String.format("Class No.:%d", classNo+1 ))
+		  .append("\n")
+		  .append(Arrays.stream(grade).mapToObj(String::valueOf).collect(Collectors.joining("\n")))  
+		  .append("\n");
+
+		System.out.print(sb);
+	}
+
+	public void printAverage(){
+		System.out.println("결과");
+		IntStream.range(0, gradeHeights.length).forEach(this::printAverage);
+	}
+
+	public void printAverage(int classNo){
+		final var sb = new StringBuilder();
+		var grade = gradeHeights[classNo];
+
+		sb.append(String.format("Class No.:%d", classNo+1 )).append("\n")
+		  .append("Height average:")
+		  .append(Arrays.stream(grade).average().getAsDouble())
+		  .append("\n");
+
+		System.out.print(sb);
+
+	}
+
+}
diff --git a/jaehong/chapter8/ManageStudent.java b/jaehong/chapter8/ManageStudent.java
new file mode 100644
index 0000000..b11ad6e
--- /dev/null
+++ b/jaehong/chapter8/ManageStudent.java
@@ -0,0 +1,24 @@
+public class ManageStudent{
+
+	public static void main(String...args){
+		Student[] student;
+		var manageStudent = new ManageStudent();
+		student = manageStudent.addStudent();
+		manageStudent.printStudent(student);
+		
+	}
+
+	public Student[] addStudent(){
+		var student = new Student[3];
+		student[0] = new Student("Lim");
+		student[1] = new Student("Min");
+		student[2] = new Student("Seok", "Seoul", "010xxxxxxx","println@kakao.com");
+		return student;
+	}
+
+	public void printStudent(Student[] student){
+		for(var std: student){
+			System.out.println(std.toString());
+		}
+	}
+}
diff --git a/jaehong/chapter8/Student.java b/jaehong/chapter8/Student.java
new file mode 100644
index 0000000..69caaf0
--- /dev/null
+++ b/jaehong/chapter8/Student.java
@@ -0,0 +1,26 @@
+
+public class Student{
+	private String name;
+	private String address;
+	private String phone;
+	private String email;
+
+	public Student(final String name, String address, String phone, String email){
+		this.name = name;
+		this.address = address;
+		this.phone = phone;
+		this.email = email;
+	}
+
+	public Student(final String name){
+
+		this.name = name;
+	}
+
+
+	@Override
+	public String toString(){
+		return name + " " + address + " " + phone + " " + email;
+	}
+
+}