add

leijing · leijing · commit bb37cd85b605 · 2017-02-27T10:48:00.000+08:00
add
diff --git a/group07/764189149/src/firstHomeWork/util/Stack.java b/group07/764189149/src/firstHomeWork/util/Stack.java
@@ -1,23 +1,22 @@
 package firstHomeWork.util;
 
-import java.util.Queue;
-
-public class Stack {
-	private ArrayList elementData = new ArrayList();
-	public void push(Object o){		
+public class Stack<E> {
+	private ArrayList<E> elementData = new ArrayList<E>();
+	public void push(E e){
+		elementData.add(e);
 	}
 	
 	public Object pop(){
-		return null;
+		return elementData.remove(elementData.size() - 1);
 	}
 	
 	public Object peek(){
-		return null;
+		return elementData.get(elementData.size() - 1);
 	}
 	public boolean isEmpty(){
-		return false;
+		return elementData.isEmpty();
 	}
 	public int size(){
-		return -1;
+		return elementData.size();
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -1,23 +1,22 @@`
`1`	`1`	`package firstHomeWork.util;`
`2`	`2`
`3`		`-import java.util.Queue;`
`4`		`-`
`5`		`-public class Stack {`
`6`		`- private ArrayList elementData = new ArrayList();`
`7`		`- public void push(Object o){`
	`3`	`+public class Stack<E> {`
	`4`	`+ private ArrayList<E> elementData = new ArrayList<E>();`
	`5`	`+ public void push(E e){`
	`6`	`+ elementData.add(e);`
`8`	`7`	`}`
`9`	`8`
`10`	`9`	`public Object pop(){`
`11`		`- return null;`
	`10`	`+ return elementData.remove(elementData.size() - 1);`
`12`	`11`	`}`
`13`	`12`
`14`	`13`	`public Object peek(){`
`15`		`- return null;`
	`14`	`+ return elementData.get(elementData.size() - 1);`
`16`	`15`	`}`
`17`	`16`	`public boolean isEmpty(){`
`18`		`- return false;`
	`17`	`+ return elementData.isEmpty();`
`19`	`18`	`}`
`20`	`19`	`public int size(){`
`21`		`- return -1;`
	`20`	`+ return elementData.size();`
`22`	`21`	`}`
`23`	`22`	`}`