Sword Point Offer (PROBLEM2-PROBLEM5) (Java)

Package Problem2;
Single-case mode implementation, note two judgments, one lock
public class Singletonclass {
Private static volatile Singletonclass instance;
Private Singletonclass () {

}
public static Singletonclass getinstance () {
if (instance = = null) {
Synchronized (Singletonclass.class) {
if (instance = = null) {
Instance = new Singletonclass ();
}
}
}
return instance;
}
}

Package Problem3;

public class Arraysearch {

public static Boolean find (int arr[][],int keyValue) {
int column = Arr.length-1;
int row = 0;
while (column>=0 && row<arr.length) {
if (arr[row][column] = = KeyValue) {
return true;
}
if (Arr[row][column] > KeyValue) {
column--;
}
else{
row++;
}
}
return false;

}
public static void Main (string[] args) {
int[][] array = new INT[4][4];
Array[0][0] = 1;
array[0][1]=2;
array[0][2]=8;
array[0][3]=9;
array[1][0]=2;
array[1][1]=4;
array[1][2]=9;
array[1][3]=12;
array[2][0]=4;
array[2][1]=7;
array[2][2]=10;
array[2][3]=13;
array[3][0]=6;
array[3][1]=8;
array[3][2]=11;
array[3][3]=15;
System.out.println (Find (array,7));
System.out.println (Find (array,5));
}
}

Package Problem4;

public class Replace {
public string Replace (string input) {
StringBuilder builder = new StringBuilder ();
if (input = = null| | input.length () ==0) {
return null;
}
for (int i = 0; i < input.length (); i++) {
if (Input.charat (i) = = ") {
Builder.append ('% ');
Builder.append (' 2 ');
Builder.append (' 0 ');
}
else{
Builder.append (Input.charat (i));
}
}
return builder.tostring ();

}
public static void Main (string[] args) {
Replace R = new replace ();
String s = "We are happy.";
System.out.println (R.replace (s));
}
}

Package PROBLEM5;

Import Java.util.Stack;

Class linknode{
Linknode Next;
int nodevalue;
}

public class Reverseprint {
public void PrintReverse (Linknode firstnode) {
stack<linknode> stack = new stack<linknode> ();
while (Firstnode!=null) {
Stack.push (Firstnode);
Firstnode = Firstnode.next;
}
while (!stack.isempty ()) {
System.out.print (Stack.pop (). NodeValue + "");
}
System.out.println ();
}
public static void Main (string[] args) {
Reverseprint r = new Reverseprint ();
Linknode Node1 = new Linknode ();
Linknode Node2 = new Linknode ();
Linknode node3 = new Linknode ();
Node1.nodevalue = 1;
Node2.nodevalue = 2;
Node3.nodevalue = 3;
Node1.next = Node2;
Node2.next = Node3;
R.printreverse (Node1);
}

}

Sword Point Offer (PROBLEM2-PROBLEM5) (Java)